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CDC vaccine panel discusses flu vaccine effectiveness, PCV20 for children

February 22, 2023

Flu vaccines have been about 49% effective in preventing severe illness in children this season, according to preliminary estimates from the Centers for Disease Control and Prevention (CDC).

The CDC provided the flu vaccine data Wednesday to its Advisory Committee on Immunization Practices (ACIP) along with data on a 20-valent pneumococcal conjugate vaccine (PCV20), which could be approved for children later this year.

Flu vaccine effectiveness

The flu vaccine effectiveness data come from several surveillance networks. The vaccine is about 68% effective in preventing influenza A-related hospitalization in children and teens and about 42% effective in preventing emergency department (ED) visits. Influenza A has been predominant this season.

In adults, effectiveness was about 39%-43% against hospitalization and 44% against an ED or urgent care visit.

Two small studies from Wisconsin found effectiveness of about 54% against an outpatient visit for influenza A among people ages 6 months-64 years and 71% against symptomatic infection in children.

So far this season, 111 pediatric flu-related deaths nationwide have been reported to the CDC. Flu activity has been low in recent weeks following an early season spike in late November/early December. However, CDC experts did not rule out the possibility of another surge.

The CDC also presented published data from several other countries that showed the effectiveness of live-attenuated influenza vaccine quadrivalent (LAIV4) was relatively similar to the traditional flu shot (inactivated influenza vaccine [IIV]). The nasal spray vaccine fell out of favor for the 2016-’17 and 2017-’18 seasons when it was deemed less effective against influenza A(H1N1) compared to IIV4. While health officials once again recommend LAIV4 equally with IIV, use has been relatively low, according to the CDC.

PCV20 vaccine

The Food and Drug Administration is reviewing Pfizer’s licensure application for PCV20 in children. Approval could come as early as this spring, which would be followed by recommendations from ACIP. It already has been authorized for adults.

The group is studying whether PCV20 should be an option for children under 2 years, who receive a three-dose series of PCV13 or PCV15 at 2, 4 and 6 months followed by a booster at 12-15 months. PCV15 was approved for children last year.

PCV20 provides broader protection than PCV13 or PCV15. However, ACIP members had some concerns about lower immunogenicity compared to PCV13 for children under 2 years. PCV20 did not meet noninferiority criteria compared to PCV13 for some of the shared serotypes after dose three, according to the CDC. However, after dose four, it was noninferior to PCV13 for all 13 shared serotypes.

ACIP member Sarah S. Long, M.D., FAAP, professor of pediatrics at Drexel University College of Medicine in Philadelphia, said the group should consider that immunogenicity doesn’t always directly correlate with effectiveness and that some serotypes are more virulent than others. She and ACIP Chair Grace M. Lee, M.D., M.P.H., both said there would be trade-offs.

“If there is concern about gain in some serotypes and the potential for loss without clarity about how it would translate in others that are relevant, it might be sort of six of one, half dozen the other,” said Dr. Lee, associate chief medical officer for practice innovation at Lucile Packard Children’s Hospital in Palo Alto, Calif. “But it does feel like at least acknowledging the indirect impact on herd immunity would be a really important aspect of the benefits of pneumococcal conjugate vaccines.”

ACIP also is considering whether PCV20 should be used for vaccination of children 2-18 years with certain underlying medical conditions. These children currently receive 23-valent pneumococcal polysaccharide vaccine in addition to PCV. For children in this age group, PCV20 was immunogenic for all 20 serotypes, but the study did not include children with underlying conditions.

ACIP is expected to continue its discussion of PCV20 later this year. In the meantime, it will meet Feb. 23 and 24 to discuss vaccines for respiratory syncytial virus, COVID, meningococcal disease and dengue.

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