Issue 1745: March 6, 2024

The committee received important informational updates, including preliminary 2023–2024 influenza vaccine effectiveness, a report from ACIP’s polio vaccine workgroup, and updates on policy considerations for RSV, meningococcal, and pneumococcal vaccines, as well as the hexavalent Vaxelis (MSP) vaccine in American Indian/Alaska Native infants.  Presentation slides are available online. Sessions are summarized below. Due to delays in seating the new ACIP chair and new members, only 7 committee members participated in the meeting. The meeting was chaired by the ACIP executive secretary and ex officio members of the committee representing key government agencies were authorized to vote. The committee is expected to be fully staffed by the next scheduled meeting in June 2024.

COVID-19 vaccine (vote)

In September 2023, CDC recommended all people age 6 months and older should receive an updated (2023–2024 Formula) COVID-19 vaccine. ACIP reviewed COVID-19 hospitalizations and vaccine coverage information collected since then. Although COVID-19 hospitalizations peaked in late December/early January, approximately 20,000 new hospital admissions and 2,000 deaths due to COVID-19 still occur each week, with highest rates of hospitalizations and deaths in people age 65 years and older. From October 2023–January 2024, over two-thirds (67%) of COVID-19 hospitalizations occurred in this age group. Uptake of the current COVID-19 vaccine in the United States has been low. Just 22% of adults have received the current vaccine, with the highest coverage reaching 43.5% in adults age 65 years and older. Vaccination rates were lowest in rural areas, among people without insurance, and in non-white populations. Since 2022, despite growing evidence of safety and benefit, the percentage of Americans who consider COVID-19 vaccine to be safe and important has declined. Fewer healthcare providers stock the vaccine, due in part to low demand and the costs of buying and storing it. Although underutilized, the current vaccine is effective and provides meaningful protection against JN.1 and other circulating variants.

The highest priority for ACIP voting members was to emphasize administration of a first dose of any current COVID-19 vaccine to all who have not already received one. However, because protection against hospitalization decreases after several months, and because COVID-19 is likely to continue to circulate through the summer, models indicate an additional dose of the current vaccine, as soon as 4 months after the initial dose could benefit those at high risk. Surveys indicate that 69% of eligible adults would get another dose, if recommended.  

The committee felt that the probability of ongoing circulation of COVID-19 through the summer and early fall, combined with waning immunity and the risk of severe disease in those age 65 years and older, justified an additional dose in this high-risk group until the next updated vaccine is recommended. ACIP voted (12 yes, 1 abstention) to recommend that people age 65 years and older who have already received a dose of the current COVID-19 vaccine should receive an additional dose of the current COVID-19 vaccine.

The additional dose should be administered at least 4 months after the previous dose. In coming days, CDC will publish on its website additional clinical considerations to help vaccination providers implement this new recommendation.
 
ACIP also discussed voting on fall 2024 COVID-19 vaccine recommendations at the June ACIP meeting. An earlier recommendation will provide manufacturers, clinicians, and public health teams with more time for integrated respiratory virus vaccination program planning for influenza, RSV, and COVID-19 this fall.

Chikungunya vaccine (vote)

Chikungunya vaccine (Ixchiq, Valneva) was licensed in the United States in November 2023 for adults at increased risk of exposure to this mosquito-borne virus. It causes a febrile rash illness with severe and sometimes persistent joint pain; illness can be more severe at older ages. Although the virus does not circulate in the United States, it can produce explosive outbreaks that affect travelers. In addition, if a breach of infection control practice occurs, it can also infect laboratory workers who handle the virus. This live attenuated vaccine is administered intramuscularly as a single dose and protects for at least a year after vaccination. During clinical trials, approximately 12% of vaccine recipients reported mild or moderate chikungunya-like adverse reactions, including transient joint pain, and 1.6% reported more significant reactions such as a fever higher than 102.1^oF.

ACIP voted on recommendations for using the vaccine in travelers and laboratory workers, as outlined below.
 
Travelers
Approximately 100–200 chikungunya cases are reported annually in U.S. travelers. Risk is greatest when traveling to an area experiencing an outbreak.

ACIP voted (12 yes, 1 abstention) to recommend chikungunya vaccine for people age 18 years and older traveling to a country or territory where there is a chikungunya outbreak. ACIP voted that vaccination may also be considered for travelers age 65 years and older with at least 2 weeks of cumulative exposure to mosquitos, or for younger adults with a cumulative mosquito exposure of 6 months or more in areas with evidence of human chikungunya transmission in the last 5 years. CDC will identify such areas, in addition to areas experiencing outbreaks, on the CDC Travelers’ Health website.

Laboratory workers
Despite the lack of a formal surveillance system for laboratory-acquired infection, at least 44 infections have been publicly reported among laboratory workers in the last 50 years, with 4 cases among U.S. laboratorians since 2015. Laboratory transmission occurs through aerosol or percutaneous exposures to chikungunya virus.

ACIP voted unanimously to recommend chikungunya vaccine for specific laboratory workers with potential for exposure to chikungunya virus in research laboratories or those who conduct certain types of diagnostic tests. Vaccination is not recommended for workers handling routine clinical samples from chikungunya-infected patients.  

Pregnant people
Chikungunya virus infection during pregnancy can result in severe and sometimes fatal illness in neonates who are infected around the time of delivery. Data are insufficient to determine the safety of the live chikungunya vaccine during pregnancy at this time; however, given the known risks of wild-type infection, CDC’s clinical guidance is pragmatic:

1. Avoid risk of exposure to chikungunya virus during pregnancy, if possible
2. In general, defer vaccination until after delivery
3. If exposure risk is high, consider vaccination during pregnancy to prevent the risk of severe adverse outcomes for the infant resulting from intrapartum transmission
4. If considering vaccination, where possible, avoid the first trimester and vaccination after 36 weeks’ gestation

Td vaccine use in place of pediatric DT for VFC program (VFC vote)
CDC recommends DTaP (diphtheria-tetanus-acellular pertussis) vaccines for all children younger than age 7 years. In rare cases of encephalopathy within 7 days after DTaP vaccination not due to another cause, further pertussis vaccination is contraindicated. In the past, CDC recommended these children complete diphtheria and tetanus vaccination with pediatric DT vaccine. DT is no longer available in the United States. To complete timely tetanus and diphtheria vaccination of young children who develop a contraindication to pertussis vaccine, CDC issued guidance allowing off-label use of Td (tetanus-reduced diphtheria) vaccine (licensed for age 7 years and older), following the same schedule that would be used for DTaP in this age group. ACIP voted (12 yes, 1 recusal) to approve a VFC program resolution permitting Td vaccine use in VFC-eligible children younger than age 7 years for whom pertussis vaccination is contraindicated. They also updated VFC resolution language on Tdap booster dose timing to align with current ACIP recommendations. The VFC resolution vote was necessary to authorize the use of VFC-purchased vaccines for these already-recommended indications.

Influenza vaccine (information)

 CDC reported that vaccination with the 2023-2024 influenza vaccine reduced the risk for medically attended influenza outpatient visits and hospitalizations among all age groups. Preliminary influenza vaccine effectiveness (VE) estimates for the 2023–2024 influenza season indicate vaccination reduced the risk of an outpatient medical visit for influenza in children by 59–67%. Adult VE for the prevention of an outpatient medical visit for influenza was lower, but significant, ranging from 33–49%.
 
Scientists presented reassuring information concerning the safety of live attenuated influenza vaccine (LAIV) in children age 5 years and older with asthma. A recent study showed no increased risk of asthma exacerbation after LAIV administration. ACIP will continue to examine this topic as it considers evidence to support removing precautions against the use of LAIV in children with asthma.
 
Global influenza surveillance presented to ACIP continues to support the FDA decision to recommend removing the B/Yamagata influenza strain from vaccines as early as the 2024-2025 season. No confirmed cases with influenza B/Yamagata viruses have been detected since March 2020.  Polio vaccine (information)
 
ACIP’s Polio Vaccine Work Group reported on its deliberations concerning whether to recommend use of a novel type 2 oral poliovirus vaccine (nOPV2) in combination with inactivated polio vaccine (IPV) as a control measure in a future U.S. polio outbreak. The nOPV2 vaccine is used for outbreak response in other countries because it can prevent transmission of virus from asymptomatic cases, but it has a non-zero risk of causing vaccine-derived paralytic polio. It is not licensed in the United States. The work group concluded that the undesirable consequences of adding nOPV2 to IPV in response to a U.S. polio outbreak likely outweigh its benefits. However, the work group noted it is possible that the size or scope of a future outbreak could shift the balance in favor of adding nOPV2.

The group also reviewed the question of how to interpret U.S. polio vaccination recommendations for children who received one or more small, intradermal doses, called “fractional doses,” of IPV (fIPV), in other countries. A mixed series of two fIPV doses and three bivalent OPV doses is recommended for children in 6 countries that account for 20% of the global birth cohort. An ACIP vote will occur at a future meeting, but evidence presented supported the WHO’s position that 2 fIPV doses should count as the equivalent of one full intramuscular IPV dose on the U.S. recommended schedule.
 
RSV adult vaccines (information)
 
ACIP discussed the safety and effectiveness of current and future RSV vaccines and plans to either affirm or revise the current RSV recommendations for older adults at the June ACIP meeting.
 
Moderna presented new information about their investigational RSV vaccine (mRNA-1345) currently being evaluated for adults age 60 years and older. The product works in the same way as the mRNA COVID-19 vaccine, using mRNA in lipid particles to deliver the “blueprint” so the recipient’s own cells make the RSV prefusion spike protein, which is the same type of protein included in current RSV vaccines. The 19,500 participants in clinical trials included people over age 80 years and people with conditions that put them at high risk of RSV complications. Preliminary results showed similar effectiveness against RSV lower respiratory tract disease (LRTD) compared to current RSV vaccines. Side effects were mostly mild injection site reactions; no cases of inflammatory neurologic disease (such as Guillain-Barre syndrome [GBS]) were identified. Consistent with the finding reported by GSK in 2023, a second dose administered 12 months later temporarily increased antibody titers, but the peak after revaccination was lower than the peak seen after the first dose. Coadministration of mRNA-1345 with mRNA COVID-19 or standard dose inactivated influenza vaccine was safe and produced a non-inferior response compared to separate administration.
 
Surveillance of community-dwelling adults age 50 and older showed that certain medical conditions substantially increased the risk of RSV-associated hospitalization. Conditions that increased risk the most included chronic kidney disease, chronic obstructive pulmonary disease (COPD), a body mass index (BMI) of 40 or greater, asthma, coronary artery disease, diabetes, and smoking. The risk of hospitalization for RSV increased gradually with increasing age among healthy people, but at every age, the presence of a high-risk condition substantially increased the RSV-associated hospitalization rate compared to healthy peers. Risk of hospitalization increased further for people with combinations of risk conditions, such as both chronic kidney disease and diabetes. These data will inform considerations of risk-based recommendations for adults age 50 and older not currently recommended to receive RSV vaccination.
 
RSV vaccine uptake among older adults in this first RSV season is estimated between 14 and 22 percent, which is a reasonable result given the challenges of implementing a new seasonal vaccine that is recommended with shared clinical decision-making (SCDM). A key question for vaccine providers and recipients is the safety of these new vaccines, particularly whether there is any association between GBS and RSV vaccination. CDC and FDA presented information from several national vaccine safety data systems. Surveillance information is not yet conclusive but suggests an association with a small increased risk of GBS in the 42 days after vaccination, with a stronger apparent signal following the Pfizer product (Abrysvo). Additional analysis is underway and necessary to verify preliminary findings. Estimates of benefits and risks generally indicate that benefits of RSV vaccination outweigh the estimated potential risks of GBS. However, the potential benefit of vaccination varies, with the greatest benefits for people with high-risk health conditions.

At this time, the ACIP work group continues to endorse its current SCDM recommendation and expects new information from ongoing studies to guide future updates, which could include an age-based recommendation for certain older adults and a risk-based recommendation for adults below that age, down to age 50 years. All decisions are contingent on results of additional safety and effectiveness studies.
 
The work group concluded that vaccination providers and patients should take into account that the best time for RSV vaccination of unvaccinated older adults is just before the start of the next RSV season, in late summer or early fall. Revaccination of adults who have already received RSV vaccine is not recommended at this time.

Meningococcal vaccine (information)
 
CDC estimates the current adolescent meningococcal vaccination schedule has prevented a total of 222 cases of serogroup C, W, or Y disease in the 12 years from 2006 through 2017. In coming months, the meningococcal work group will consider revising the routine adolescent meningococcal ACWY (MenACWY) and MenB vaccination schedules in response to updated disease epidemiology and the anticipated licensure of a second pentavalent MenABCWY vaccine option (from GSK) in addition to the current MenABCWY option (Penbraya, Pfizer).
 
Even before MenACWY vaccine introduction, the lowest risk of meningococcal disease was at age 11–12 years, but the age was selected because it is when other adolescent vaccines are routinely given. The greatest risk during adolescence is in late adolescence, at age 18 or older. New studies show a greater risk for MenB disease during college, especially among 4-year college students, with greatest risk among first-year students, on-campus residents, and students involved in Greek life.
 
Future work group considerations include the effect of dropping the 11–12-year-old dose in favor of vaccination at older ages, when the risk of disease is greater. The work group will also consider whether to change the age for MenB recommendations and whether to make MenB recommendations routine. Discussion among the committee and liaisons reflected disparate views, and members expressed the need for additional data.

Pneumococcal vaccine (information)
 
ACIP reviewed information on future pneumococcal conjugate vaccines (PCVs). Merck’s investigational PCV21 (V116) is expected to be licensed for adults in coming months, and investigational PCVs covering 24 and 31 serogroups may be licensed in the near future. The work group is weighing how PCV recommendations will continue to evolve in response to new products and changes in the prevalence of disease caused by serogroups included in vaccines. For example, PCV20 (Prevnar20, Pfizer) contains 10 serogroups excluded from PCV21, which includes 11 serogroups not in PCV20. Among adults, PCV21 would cover serogroups causing 81–85% of current cases of U.S. invasive pneumococcal disease (IPD); PCV20 covers serogroups causing 54–58% of adult IPD.
 
Phase 3 studies of PCV21 demonstrated the vaccine was effective and safe, with a side effect profile similar to other PCV vaccines. When administered at the same time as quadrivalent inactivated influenza vaccine (QIV), the immune response was non-inferior to sequential administration for 20 of 21 serogroups and for 3 of 4 influenza strains (all except A/H3).
 
Safety studies of PCV20 were reviewed. Potential safety signals related to GBS in the Vaccine Adverse Event Reporting System (VAERS) require evaluation in other more robust safety systems, such as the Vaccine Safety Datalink (VSD), and these reviews are underway. No GBS signal for PCV20 has been detected in Medicare safety monitoring systems. Monitoring is ongoing.
 
The session concluded with questions the work group will consider beyond adding PCV21 as an option for adults currently recommended to receive PCV. New policy questions include whether to recommend PCV21 for adults age 50–64 years who do not have a risk-based recommendation, and whether an age-based recommendation might be considered down to age 19 years. Further data will be presented on these questions at future meetings.

Use of hexavalent Vaxelis vaccine in American Indian/Alaska Native populations (information)
 
For reasons not entirely understood, American Indian/Alaska Native (AI/AN) children have historically had higher rates of Hib disease than the general population, with onset earlier in life. For this reason, AI/AN children are preferentially recommended to receive PedvaxHIB (Merck), the only available Hib vaccine that leads to protective immunity after the first dose. PedvaxHIB is given at age 2 months and 4 months, with a booster at 12–15 months.
 
Vaxelis (MSP) is a hexavalent combination vaccine (DTaP-IPV-Hib-HepB) licensed and recommended as an option for HepB vaccination and for the first three doses of the DTaP, polio (IPV), and Hib vaccine series, routinely given at the 2-, 4-, and 6-month infant immunization visits.  Vaxelis contains the same type of Hib vaccine as PedvaxHIB (PRP-OMP), but has a smaller quantity of Hib antigen per dose. When first licensed, Vaxelis was not given a preferential recommendation for use in AI/AN infants because it was not known whether Vaxelis could produce protective immunity after the first dose. 
 
Research recently conducted in Navajo and Alaska Native populations demonstrated that Vaxelis produced an equivalent or superior immune response in study subjects when compared to PedvaxHIB, including after the first dose. Use of Vaxelis could reduce the number of injections needed in the first year of life from as many as 12 to as few as 5, which could improve series completion rates. ACIP members expect to vote on Vaxelis as an option for AI/AN infants at the June 2024 meeting.

Next meeting
The next scheduled ACIP meeting will be held June 26–28, 2024, although additional emergency meetings may be announced before that time. Information about past and future ACIP meetings may be found on the ACIP website.  

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Immunize.org created and posted new Spanish translations of four patient resources on improving the vaccination experience. Use these to support anxious patients of all ages and increase their confidence in accepting vaccination. The resources include:

• Addressing Vaccination Anxiety for Children: Strategies for Vaccine Recipients and Caregivers (view in Spanish)
• Addressing Vaccination Anxiety for Infants and Toddlers: Strategies for Parents and Caregivers (view in Spanish)
• Addressing Vaccination Anxiety in Adolescents and Adults: Strategies for Vaccine Recipients and Caregivers (view in Spanish)
• Fainting Related to Vaccination: What You Need to Know (view in Spanish)

         

Related Links

• Immunize.org: Improving the Vaccination Experience main page
• Immunize.org: Clinical Resources: Addressing Vaccination Anxiety main page
• Immunize.org: Clinical Resources in Spanish 
• Immunize.org: Clinical Resources A–Z main page, where you can filter by topic, vaccine, language, or other criteria