Ask the Experts: All Questions

Ask the Experts is one of our most popular destinations for healthcare professionals. Our experts provide clear, easy-to-understand answers to commonly asked questions about vaccines and their use.

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Results (1355)

As soon as possible, even if it is the same day.

Last reviewed: March 31, 2022

Twinrix (GSK) is an inactivated combination vaccine containing both hepatitis A virus (HAV) and hepatitis B virus (HBV) antigens. The vaccine contains 720 EL.U. of hepatitis A antigen (half of the Havrix adult dose) and 20 mcg of hepatitis B antigen (the full Engerix-B adult dose).

In the U.S., Twinrix is licensed for use in people who are age 18 years or older. It can be administered to people who are at risk for both hepatitis A and hepatitis B, such as certain international travelers, people with HIV infection, people with chronic liver disease not caused by hepatitis B, men who have sex with men, people who use drugs, or to people who simply want to be immune to both diseases. Primary immunization consists of 3 doses given intramuscularly on a 0-, 1-, and 6-month schedule. In 2007, the FDA also approved a 4-dose schedule for Twinrix. It consists of 3 doses given within 4 weeks, followed by a booster dose at 12 months (0, 7 days, 21–30 days, and 12 months). The 4-dose schedule could benefit individuals needing rapid protection from hepatitis A and hepatitis B, such as people traveling to high-prevalence areas imminently.

Twinrix cannot be used for postexposure prophylaxis.

Last reviewed: June 25, 2023

Yes. Poorer immune response rates are seen in infants who complete the vaccination series prior to age 6 months. Do not count dose #3, which you gave at age 4 months. Repeat dose #3 when the infant is at least 6 months of age (no earlier than age 24 weeks).

Last reviewed: July 21, 2023

Yes. CDC has published an appendix to its interim clinical considerations for the use of COVID-19 vaccines to address a wide range of errors in vaccine administration. It includes a detailed table outlining actions to take after an error has occurred: www.cdc.gov/vaccines/covid-19/clinical-considerations/interim-considerations-us-appendix.html#appendix-b.

Categories of errors covered in the CDC table include:

  • Site/route
  • Age
  • Product and dosage
  • Incorrect intervals
  • Interchanging product types when not recommended
  • Incorrect diluent (certain Pfizer-BioNTech formulations)
  • Use of diluent when not indicated

Ask the Experts refers our readers to this CDC table for the most current and comprehensive guidance on COVID-19 vaccine administration errors and how to manage them. For all vaccine administration errors the following steps are recommended: inform the patient of the error, report the error to VAERS (https://vaers.hhs.gov) unless CDC’s guidance states that the error does not need to be reported, evaluate why the error occurred, and implement strategies to prevent future errors.

Last reviewed: August 31, 2024

A previous history of chickenpox disease, even recent disease, is not known to interfere with the immune response to different vaccines. To review the true contraindications and precautions to vaccination, consult the appendix of the CDC Recommended Child and Adolescent Immunization Schedule (www.cdc.gov/vaccines/schedules/hcp/imz/child-adolescent.html).

CDC’s “General Best Practice Guidelines for Immunization” also contains the table of contraindications and precautions, in addition to a useful table titled “Conditions incorrectly perceived as contraindications or precautions to vaccination (i.e., vaccines may be given under these conditions)”. Both tables are available at www.cdc.gov/vaccines/hcp/acip-recs/general-recs/contraindications.html, Tables 4-1 and 4-2.

Last reviewed: February 19, 2024

All meningococcal conjugate vaccines (MenACWY, MenB, MenABCWY) should be administered by the intramuscular route.

Last reviewed: November 15, 2024

No. ACIP does not identify people who use smokeless tobacco products or vaping as being at increased risk for invasive pneumococcal disease or as being in a risk group recommended for vaccination.

Last reviewed: November 13, 2024

No. CDC and ACIP express no preference for preservative-free vaccine for infants or any other group of vaccine recipients.

No scientific evidence exists that thimerosal in vaccines is a cause of adverse events unless the patient has a systemic allergy to thimerosal. However, some states have enacted legislation that restricts the use of thimerosal-containing vaccines. Check with your state immunization program to see if your state is one of them (www.immunize.org/official-guidance/state-policies/state-resources/)

Last reviewed: August 11, 2024

The recipient should be informed of the error, and RSV vaccine should be administered as recommended. A 50-mg or 100-mg MFS dose of antibody is very small compared to the body weight of an adult and you should not assume the dose would have any protective effect. There is no defined waiting period after antibody administration for vaccine administration. Facilities that stock RSV vaccine and nirsevimab (Beyfortus, Sanofi) should put systems and procedures in place to prevent this type of error, including staff training and clear labeling and warnings in storage units.

CDC strongly encourages reporting of this medication error and any suspected adverse events following the error to the Vaccine Adverse Event Reporting System (VAERS) at https://vaers.hhs.gov if the antibody was administered at the same visit as vaccines. If antibody was administered alone, report the incident to MedWatch online (www.fda.gov/medwatch), by fax, by mail, or by contacting FDA at 1-800-FDA-1088.

Last reviewed: August 25, 2024

No. Even a woman found to be infected with a strain of HPV that is present in the vaccine could receive protection from the other strains in the vaccine.

Last reviewed: March 2, 2024

Breastfeeding is NOT a precaution to vaccination with Shingrix (RZV). Recombinant vaccines such as RZV pose no known risk to mothers who are breastfeeding or to their infants. Clinicians should consider vaccination without regard to breastfeeding status if RZV is otherwise indicated.

Last reviewed: March 9, 2022

There is no known risk associated with MMR or varicella vaccination in someone with selective IgA or IgM deficiency. It is possible that the immune response may be weaker, but the vaccines are likely effective.

Last reviewed: May 16, 2023

Approximately 5 to 15% of susceptible people who receive MMR vaccine will develop a low-grade fever and/or mild rash 7 to 12 days after vaccination. However, the person is not infectious, and no special precautions ( such as exclusion from work) need to be taken.

Last reviewed: June 19, 2023

Empty or expired vaccine vials are considered medical waste and should be disposed of according to state regulations.

Last reviewed: December 28, 2022

No. CDC does not recommend repeating the dose of any COVID-19 vaccine in circumstances where the dose is administered in an incorrect route or an incorrect site (i.e., not in the deltoid or anterolateral thigh). In the case of a subcutaneous injection, the patient should be advised of the possibility of self-limited local or systemic side effects.

Last reviewed: August 31, 2024

Vaccination of the parents against pertussis after the baby is born is not optimal, but it may be helpful and should be done if the parents have not previously received Tdap, regardless of when they last received Td vaccination. It takes about 2 weeks after Tdap receipt for the parents to have protection against pertussis. Once the parents have protection, they are is less likely to transmit pertussis to the infant. However, the newborn remains at risk of contracting pertussis from others, including siblings, grandparents, and other caregivers. They should be counseled about the importance of Tdap vaccination of the mother during future pregnancies. See CDC’s web page for more information: www.cdc.gov/pertussis/hcp/vaccine-recommendations/vaccinating-pregnant-patients.html.

Last reviewed: March 31, 2022

If an infant received an adult dose of HepB (contains twice the antigen in a dose of the pediatric formulation), the dose can be counted as valid and does not need to be repeated. Hepatitis B vaccines are very safe vaccine and no unusual adverse events would be expected because of this administration error. The next (age appropriate) dose should be given on the usual schedule.

Last reviewed: July 21, 2023

People with a metabolic disease, including diabetes, should receive annual influenza vaccination with an age-appropriate inactivated or recombinant influenza vaccine.

Last reviewed: August 11, 2024

Vaccination will have the most benefit if administered in late summer or early fall, just before the RSV season. In most of the continental United States, this corresponds to vaccination during August–October.

If you have an opportunity to vaccinate an eligible patient and are concerned that there will not be an opportunity to vaccinate during an ideal time of year, you may administer RSV vaccine at any time of year. A meaningful degree of protection after vaccination should last at least two years.

Last reviewed: August 25, 2024

No, unless chronic lung disease is present, which puts them at increased risk of pneumococcal disease. PCV20 or PCV21 alone or PCV15 followed one year later by PPSV23 is recommended for current smokers of cigarettes age 19 through 49 years (see  www.cdc.gov/mmwr/volumes/71/wr/pdfs/mm7104a1-H.pdf). 

Last reviewed: November 13, 2024

The liquid vaccine component (the diluent) of Menveo contains the C, W-135, and Y serogroups, and the lyophilized vaccine component (the freeze-dried powder) contains serogroup A. Because the patient received only the diluent, he or she is not protected against invasive meningococcal disease caused by N. meningitidis serogroup A.

Invasive disease with N. meningitidis serogroup A is very rare in the United States but is more common in some other countries. If the recipient (of the C-Y-W135 “diluent” only) is certain not to travel outside the United States, then the dose does not need to be repeated. However, if the recipient plans to travel outside the United States the dose should be repeated with correctly reconstituted Menveo, the one-vial formulation of Menveo that does not require reconstitution, or with a dose of another brand of MenACWY. There is no minimum interval between the incorrect dose and the repeat dose.

Last reviewed: November 15, 2024

Once they are no longer acutely ill, they can be vaccinated with Shingrix. There is no evidence that vaccine will have therapeutic effect for a person with existing zoster or postherpetic neuralgia.

Last reviewed: March 9, 2022

Yes, as a healthcare professional, this person should get a second dose of MMR to ensure she is immune to rubella. There is no harm in providing MMR to a person who is already immune to one or more of the components. If she developed measles only one day after getting her first MMR, she must have been exposed to the disease prior to vaccination.

Last reviewed: June 19, 2023

Varicella vaccine is very safe. About 20% of vaccine recipients will have minor injection site complaints, such as pain, swelling, or redness. Fewer than 5% of recipients develop a localized or generalized varicella-like rash 5 to 26 days after vaccination. These rashes have an average of 2 to 5 lesions, and may be maculopapular rather than vesicular. Fever following varicella vaccine is uncommon.

Last reviewed: May 16, 2023

Yes. Tdap can be administered with all other vaccines that are indicated (e.g., meningococcal conjugate vaccine, hepatitis B vaccine, MMR). Each vaccine should be administered at a different anatomic site using a separate syringe.

Last reviewed: March 31, 2022

No. Twinrix contains 50% less hepatitis A antigen component than Havrix, GSK’s monovalent hepatitis A vaccine [720 vs. 1440 El. U.], so the patient would not receive the recommended dose of hepatitis A vaccine antigen. For this reason, 3 doses of Twinrix must comprise the series.

Last reviewed: June 25, 2023

The minimum age for the last dose of HepB is age 24 weeks (the minimum age is the youngest age that is acceptable for giving a vaccine and having it “count” as a valid dose.) This allows healthcare providers more flexibility in administering HepB should a parent bring an infant in for a well-baby check before the infant reaches a full 6 months of age. If the third dose is given prior to age 24 weeks the dose should not be counted. Poorer response rates are seen in infants who complete the vaccination series prior to age 24 weeks. The third dose should be repeated when the infant is at least age 24 weeks.

Last reviewed: July 21, 2023

In clinical trials of 9vHPV (Gardasil 9, Merck) involving more than 15,000 vaccine recipients, most adverse events were mild or moderate injection site-related pain, swelling, and redness. Up to 40% reported one of these injection site reactions after vaccination, and they were more common among females compared to males. Injection site reactions also were more likely following the second or third dose compared to the first dose. Fewer than 10% of recipients reported fever.

Last reviewed: March 2, 2024

Yes. MenACWY and MenB vaccines can be given at the same visit or at any time before or after the other. The pentavalent MenABCWY vaccine Penbraya (Pfizer) may be administered as an option for people age 10 or older who need both MenB-FHbp (Trumenba, Pfizer) and MenACWY vaccination at the same visit. For people age 10 years or older at increased risk of meningococcal disease, Penbraya may be used for additional MenACWY and MenB doses (including booster doses) if both would be given on the same clinic day and at least 6 months have elapsed since most recent Penbraya dose.

Last reviewed: November 15, 2024

Yes. People with multiple sclerosis should be vaccinated against influenza. Multiple sclerosis is not a contraindication to any vaccine, including influenza vaccines.

Last reviewed: August 11, 2024

Aim for nirsevimab (Beyfortus, Sanofi) administration in the first week of life for infants born shortly before or during the RSV season (typically October through March). Infants with prolonged birth hospitalizations due to prematurity or other causes should receive nirsevimab shortly before or promptly after discharge.

Infants younger than age 8 months born outside of the RSV season and older infants or toddlers at high risk who are recommended to receive nirsevimab in their second RSV season, should aim to receive nirsevimab shortly before the start of the RSV season (typically October).

If the ideal timing is missed, age-eligible infants and children who have not yet received a dose may be immunized at any time during the RSV season.

If you are located in Alaska, Hawaii, or another region of the United States with a different pattern of RSV circulation, follow the timing guidance of your state or territorial public health officials.

Last reviewed: August 25, 2024

No. ACIP does not designate people who smoke marijuana, but not cigarettes, as being in a risk group for vaccination. ACIP has not been presented evidence of an increased risk of pneumococcal disease among regular marijuana smokers.

Last reviewed: November 13, 2024

Yes. CDC recommends that all children age 0 through 18 years be fully vaccinated against hepatitis B. This recommendation is also endorsed by AAP and AAFP and is published as part of the annual Recommended Childhood and Adolescent Immunization Schedule (www.cdc.gov/vaccines/schedules/hcp/child-adolescent.html). Vaccination should be initiated for children and teenagers not previously vaccinated and vaccination completed for all those whose vaccine series is incomplete.

All children and adolescents younger than age 19 years (including internationally adopted children) who were born in Asia, the Pacific Islands, Africa, or other intermediate or high-endemic countries or who have at least one parent who was born in a high-endemic area should be tested for HBsAg and should complete the vaccine series if they were not previously vaccinated or were incompletely vaccinated.

Last reviewed: July 21, 2023

There is no waiting period for administering Shingrix following transfusion. Shingrix contains no live virus so may be given at any time after receipt of a blood product.

Last reviewed: March 9, 2022

If you believe the child had varicella disease (that is, breakthrough varicella) after the first dose, the child does not need another dose. If you are uncertain whether the child had varicella or a rash related to varicella vaccination, the second dose should be administered on schedule. If in doubt, give the second dose. If this was a case of breakthrough varicella, a second dose will not be harmful.

Last reviewed: May 16, 2023

The DTaP recipient received the appropriate amount of tetanus toxoid and MORE diphtheria toxoid and pertussis antigen than is recommended. Count the dose as Tdap, but take measures to prevent this error in the future. The patient does not need a repeat dose of Tdap.

Last reviewed: March 31, 2022

Immune globulin (IG, GamaSTAN, Grifols Therapeutics) is a sterile preparation of concentrated antibodies (i.e., immunoglobulins) made from pooled human plasma processed by cold ethanol fractionation. GamaSTAN is the only IG product licensed in the United States for the prevention of hepatitis A virus (HAV) infection. Only plasma that has tested negative for hepatitis B surface antigen, antibody to human immunodeficiency virus (HIV), and antibody to hepatitis C virus (HCV) is used to produce IG. In addition, the Food and Drug Administration requires that the process used to produce IG include a viral inactivation step or that final products test negative for HCV-RNA by polymerase chain reaction. Anti-HAV concentrations differ among IG lots and decreasing concentrations have been observed over the past 30 years, probably because of the decreasing prevalence of previous HAV infection among plasma donors. In 2017, the dosing of GamaSTAN for HAV prevention was increased to reflect this change in anti-HAV potency.

Last reviewed: June 25, 2023

The dose should be repeated. If the expired dose is a live virus vaccine, you should wait at least 4 weeks after the previous (expired) dose was given before repeating it. If the expired dose is not a live vaccine, the dose should be repeated as soon as possible. Although simply repeating the dose is preferred, serologic testing to check for immunity after certain vaccinations (e.g., measles, rubella, varicella, hepatitis A) may be accepted.

Last reviewed: December 28, 2022

Contraindications:

  • history of a severe (anaphylactic) reaction to any vaccine component or following a previous dose of MMR (see specific package insert for details: www.fda.gov/vaccines-blood-biologics/vaccines/vaccines-licensed-use-united-states)
  • pregnancy
  • severe immunosuppression from either disease or therapy
  • family history of altered immunocompetence, unless verified clinically or by laboratory testing as immunocompetent

Precautions:

  • receipt of an antibody-containing blood product in the previous 11 months, depending on the type of blood product received. Specific intervals vary by product type. See www.cdc.gov/vaccines/hcp/acip-recs/general-recs/timing.html, Table 3-6, for more information on this issue.
  • history of thrombocytopenia or thrombocytopenic purpura
  • moderate or severe acute illness with or without fever
  • need for tuberculin skin testing or interferon gamma release assay (IGRA) testing

Important details about the contraindications and precautions for MMR vaccine are in the 2013 MMR ACIP statement, available at www.cdc.gov/mmwr/pdf/rr/rr6204.pdf.

Last reviewed: June 19, 2023

No. Since 2006, well over 100 million doses of HPV vaccine have been administered in the United States. Among all reports to the Vaccine Adverse Event Reporting System (VAERS) following HPV vaccines, the most frequently reported symptoms overall were dizziness; fainting; headache; nausea; fever; and pain, redness, and swelling in the arm where the shot was given. Although deaths have been reported among vaccine recipients none has been conclusively shown to have been caused by the vaccine. Occurrences of rare conditions, such as Guillain-Barré Syndrome (GBS) have also been reported among vaccine recipients but there is no evidence that HPV vaccination increased the rate of GBS above what is normally expected in the population.

CDC, working with the FDA and other immunization partners, continues to monitor the safety of HPV vaccines. You can find complete information on this and other vaccine safety issues www.cdc.gov/vaccine-safety/vaccines/hpv.html and at www.cdc.gov/vaccine-safety/vaccines/hpv.html.

Last reviewed: March 2, 2024

The most common adverse events following MenACWY vaccination were injection site pain, swelling or redness. Other reported symptoms included malaise and headache.

Last reviewed: November 15, 2024

Although some studies have demonstrated a transient increase in replication of HIV following inactivated influenza vaccine, other studies have not found this. This temporary increase in HIV titer has not been associated with deterioration in either T-lymphocyte counts or clinical condition. Annual influenza vaccination with an age-appropriate injectable influenza vaccine benefits HIV-infected people.

Last reviewed: August 11, 2024

CDC has published an immunization information statement (IIS) for nirsevimab (Beyfortus, Sanofi) that is the equivalent of the vaccine information statement (VIS) for vaccines. Just as with a VIS, providers should give the IIS to the parent or caregiver before immunization and document it in the medical record.

Access the current nirsevimab IIS and translations in numerous languages from Immunize.org at: www.immunize.org/vaccines/vis/iis-rsv/.

Last reviewed: August 25, 2024

In the pneumococcal vaccine recommendations for adults that were updated January 28, 2022, the many risk groups for pneumococcal disease were combined into one group with respect to vaccine recommendations. All are now recommended to receive PCV20 or PCV21 alone or PCV15 followed by PPSV23 one year later. ACIP no longer recommends the use of PPSV23 alone for any adult. Cigarette smokers too young for routine age-based vaccination recommendations who received PPSV23 alone in the past may now receive a dose of any recommended pneumococcal conjugate vaccine option (PCV15, PCV20, or PCV21) at least one year after their dose of PPSV23.

Last reviewed: November 13, 2024

Yes. Shingrix can be administered in this situation.

Last reviewed: March 9, 2022

People with medical conditions that contraindicate measles immunization depend on high MMR vaccination coverage among those around them. To help prevent the spread of measles virus, make sure all your staff and patients who can be vaccinated are fully vaccinated according to the U.S. immunization schedule. Also, encourage patients to remind their family members and other close contacts to get vaccinated if they are not immune.

If patients who cannot get MMR vaccine are exposed to measles, CDC has guidelines for immune globulin for post-exposure prophylaxis which can be found at www.cdc.gov/mmwr/pdf/rr/rr6204.pdf.

Last reviewed: June 19, 2023

Transmission of varicella vaccine virus is a rare event, and appears to occur only when the vaccinated person develops a vesicular rash. A maculopapular rash 2 weeks after varicella vaccine may not have been caused by the vaccine. If the rash were caused by the vaccine, the risk of transmission is very small; however, the child should avoid close contact with people who do not have evidence of varicella immunity and who are at high risk of complications of varicella, such as immunocompromised people, until the rash has resolved.

Last reviewed: May 16, 2023

IG provides protection against HAV infection through passive transfer of antibody. Depending on the IG dosage, protection lasts from 1 to 2 months.

When administered for preexposure prophylaxis, a dose of 0.1 mL/kg will provide protection for up to 1 month and a dose of 0.2 mL/kg will provide protection for up to 2 months. If longer term protection is required and vaccination is contraindicated, a dose of 0.2 mL/kg can be repeated every 2 months. There is no maximum number of times the bimonthly doses of IG may be repeated as long as hepatitis A prophylaxis is required.

For postexposure prophylaxis, the recommended dosage is 0.1 mL/kg.

Last reviewed: June 25, 2023

Yes. The National Vaccine Injury Compensation Program includes payment for injuries determined to have occurred following vaccination with a vaccine routinely recommended for children in the United States. The recipient can be of any age, but the vaccine must be routinely recommended for children and teens through age 18 years. MenACWY is routinely recommended for children so it is included in the program. More information about the program and the covered vaccines is at www.hrsa.gov/vaccine-compensation/covered-vaccines/index.html.

Last reviewed: November 15, 2024

Revaccination of individuals who are up to date on Tdap immunization with an additional dose of Tdap during a pertussis outbreak is currently not recommended.

Last reviewed: March 31, 2022

Nearly all vaccines have been reported to be associated with fainting (syncope). Post-vaccination syncope has been most frequently reported after three vaccines commonly given to adolescents (HPV, MenACWY, and Tdap). However, it is not known whether the vaccines are responsible for post-vaccination syncope or if the association with these vaccines simply reflects the fact that adolescents are generally more likely to experience syncope due to needle- and pain-related anxiety.

Syncope can cause serious injury. Falls that occur due to syncope after vaccination can be prevented by having the vaccinated person seated or lying down. The person should be observed for 15 minutes following vaccination. For additional information about vaccination-associated syncope, see Immunize.org’s clinical resource, Vaccination-Related Syncope: Information for Healthcare Personnel at www.immunize.org/wp-content/uploads/catg.d/p4260.pdf.

Last reviewed: March 2, 2024

Periodically verify whether you are using the most current available documents by checking Immunize.org’s regularly updated Checklist of Current Versions of U.S. COVID-19 Vaccination Guidance and Clinic Support Tools: www.immunize.org/catg.d/p3130.pdf. This resource is updated at least monthly with the dates of the most currently available materials from CDC and FDA.

There is normally a delay between the public announcement of a change in COVID-19 vaccination recommendations and the release of updated CDC guidance documents that incorporate the change. Information is generally updated first on the CDC web page: Use of COVID-19 Vaccines in the United States (www.cdc.gov/vaccines/covid-19/clinical-considerations/covid-19-vaccines-us.html).

Last reviewed: August 31, 2024

In November 2015, FDA licensed Fluad (aIIV, CSL Seqirus), an MF59-adjuvanted inactivated influenza vaccine, for people age 65 years and older. Fluad is the first adjuvanted influenza vaccine marketed in the U.S. An adjuvant is a substance added to a vaccine to increase the immune response to vaccination. The MF59 adjuvant is based on squalene, an oil that occurs naturally in many plants and animals. Fluad has been used in Europe since 1997 and is approved in many other countries. In contrast to Fluzone High-Dose (HD-IIV, Sanofi), Fluad is a standard-dose vaccine, containing 15 mcg of hemagglutinin per virus per dose.

Last reviewed: August 11, 2024

Yes, you should report administration of nirsevimab (Beyfortus, Sanofi) to your state immunization information system (IIS, or “registry”) as you would report vaccine administration. Contact your state immunization program if you have specific questions about reporting to your state immunization information system.

Last reviewed: August 25, 2024

Yes. There are data that show adequate seroprotection using this schedule in young adults. If this schedule is used, you should be aware that the studies were in young adults and might not translate to older adults (age 40 years or older). There are other schedules that offer flexibility in vaccination as well. View www.immunize.org/catg.d/p2081.pdf for a review of different schedules.

Last reviewed: July 21, 2023

Yes. Pneumococcal vaccination is recommended for adults age 19 through 49 years with all types of asthma.

Among children age 2 through 18 years, only those with moderate persistent or severe persistent asthma (regardless of high-dose oral corticosteroids use) should be evaluated for additional pneumococcal vaccine doses beyond the routine age-based schedule. Specific recommendations depend on age and the recipient’s specific pneumococcal vaccination history, including prior doses of any pneumococcal vaccine except PCV7. Prior doses of PCV7 may be ignored for the purposes of determining doses due now.

Last reviewed: November 13, 2024

Yes. Acyclovir, famciclovir, and valacyclovir are antiviral drugs that are active against herpesviruses. These drugs will have no effect on Shingrix, which does not contain live varicella virus.

Last reviewed: March 9, 2022

There is no known risk associated with MMR or varicella vaccination in someone with selective IgA or IgM deficiency. It is possible that the immune response may be weaker, but the vaccines are likely effective.

Last reviewed: June 19, 2023

You cannot distinguish a mild case of varicella disease from a rash caused by the vaccine. The child may have been infected with varicella at about the same time s/he was vaccinated. The conservative approach would be to treat the child as if s/he had chickenpox and restrict her/his activities until all the lesions crust.

Last reviewed: May 16, 2023

Yes. Tdap vaccination is routinely recommended to be given at 27 through 36 weeks’ gestation during every pregnancy. This CDC recommendation is endorsed by the American College of Obstetricians and Gynecologists (ACOG), the American College of Nurse-Midwives (ACNM), the American Academy of Pediatrics (AAP), and the American Academy of Family Physicians (AAFP). Tdap given during one pregnancy will not provide sufficient protection for subsequent pregnancies. In June 2011 ACIP first voted to recommend that pregnant people who have never received the Tdap vaccine be vaccinated to optimize the concentration of maternal antibodies transferred to the fetus. ACIP made this recommendation with the goal of protecting newborns with maternal antibodies and decreasing the risk of transmission of pertussis to infants shortly after birth. In October 2016, ACIP voted to recommend administering Tdap vaccination early in the 27- through 36-week “window” to maximize passive antibody transfer to the infant. Mothers who have never received Tdap and who do not receive it during pregnancy should receive it immediately postpartum.

Fewer babies are hospitalized for pertussis when Tdap is given during pregnancy rather than during the postpartum period. A large U.S. study found an 85% reduction in the risk of pertussis in infants under 2 months of age whose mothers were vaccinated with Tdap at 27 through 36 weeks’ gestation, compared to infants whose mothers were vaccinated in the hospital immediately following delivery.

When a mother gets Tdap during pregnancy, maternal pertussis antibodies transfer to the newborn, protecting the baby against pertussis in early life, before the baby is old enough to have received vaccination with DTaP. Tdap also protects the mother, making it less likely that she will get infected with pertussis during or after pregnancy.

Recommendations for the use of Tdap in pregnancy are covered in detail here: www.cdc.gov/mmwr/volumes/67/rr/pdfs/rr6702a1-H.pdf, pages 22–23.

Last reviewed: March 31, 2022

Intramuscular IG is available in single-use vials (2 mL and 10 mL). It should be administered intramuscularly, preferably in the anterolateral aspects of the upper thigh and the deltoid muscle of the upper arm. Do not use the gluteal region as an injection site because of the risk of injury to the sciatic nerve.

Last reviewed: June 25, 2023

As with all vaccines, a severe allergic reaction (for example, anaphylaxis) to a vaccine component or to a prior dose is a contraindication to further doses of that vaccine. A moderate or severe acute illness is a precaution; vaccination should be deferred until the person’s condition has improved. Because MenACWY is an inactivated vaccine, it can be administered to people who are immunosuppressed as a result of disease or medications; however, response to the vaccine might be less than optimal.

Last reviewed: November 15, 2024

HPV vaccine should be stored at refrigerator temperature between 2°C and 8°C (36°F and 46°F). The vaccine must not be frozen and must not be used if it has been frozen. Protect the vaccine from light. Administer as soon as possible after being removed from refrigeration. The manufacturer package insert contains additional information and can be found at https://www.immunize.org/official-guidance/fda/pkg-inserts/. For complete information on vaccine storage and handling best practices and recommendations, please refer to CDC’s Vaccine Storage and Handling Toolkit at www.cdc.gov/vaccines/hcp/admin/storage/toolkit/storage-handling-toolkit.pdf.

Last reviewed: March 2, 2024

Yes. Aging decreases the body’s ability to develop a good immune response after getting influenza vaccine, which places older people at greater risk of severe illness from influenza.

After years of review and deliberation, ACIP voted in June 2022 to recommend that all adults age 65 and older should preferentially receive one of the three different vaccine products that evidence suggests are likely to perform better than standard dose, unadjuvanted vaccines: Flublok recombinant influenza vaccine (RIV, Sanofi), Fluad adjuvanted vaccine (aIIV, CSL Seqirus), or Fluzone High-Dose vaccine (HD-IIV, Sanofi). However, if none of these three vaccines is available at the time of vaccination, any age-appropriate influenza vaccine may be administered.

For a thorough review of the evidence for this recommendation, see the 2022 ACIP recommendations for influenza vaccination: www.cdc.gov/mmwr/volumes/71/rr/pdfs/rr7101a1-H.pdf.

Last reviewed: August 11, 2024

It is important that all healthcare providers, both prenatal and pediatric, ensure that maternal RSV vaccination status is clearly documented and communicated. Prenatal care providers and birthing hospitals should ensure maternal RSV vaccination is reported to state immunization information systems (registries) and documented in maternal and newborn health records. It is also important to provide the pregnant person with a personal record of immunization.

Failure to document and communicate maternal RSV vaccination may result in extra work for pediatric offices and families to obtain records or in unnecessary administration of nirsevimab (Beyfortus, Sanofi),  at a retail cost of approximately $450 per dose.

RSV vaccination is recommended only once, so the history of RSV vaccination is also important information for future pregnancies when the mother would need to be counseled that RSV vaccination is not an option and the infant should receive nirsevimab after delivery for RSV prevention.

Last reviewed: August 25, 2024

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