2023 saw important firsts in vaccine approvals and more are expected this year

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Last year saw the approval of several firsts in vaccine approvals, including the first vaccines to prevent respiratory syncytial virus (RSV) in older adults and infants and a first vaccine to prevent the mosquito-borne virus chikungunya.

Vaccinations are among the most important public health tools for preventing serious illness, avoiding hospitalizations and saving lives. During the COVID-19 pandemic, vaccine technology made a huge leap forward with the introduction of messenger RNA (mRNA) vaccines. COVID-19 vaccines developed by BioNTech/Pfizer and Moderna use mRNA instead of weakened viruses or virus fragments to teach the body’s immune system how to respond when presented with an infection.

Innovation in the vaccine area continues. In 2023, the FDA approved six vaccines, including several important firsts. (See list below.)

In the area of respiratory diseases, the first two vaccines for respiratory syncytial virus (RSV) were approved for older adults and a separate vaccine was approved to prevent RSV infections in infants. RSV is a common respiratory virus that usually causes mild, cold-like symptoms, but it can lead to serious respiratory illness and increased hospitalizations. It results in 14,000 deaths annually among those over the age 65 and about 58,000 hospitalizations of infant younger than 1, according to the National Institute of Allergy and Infectious Disease.

GlaxoSmithKline’s Arexvy, approved for adults in early May 2023, is an adjuvanted vaccine, which means it contains an ingredient to increase immune response. The second adult vaccine was approved a few weeks later. Pfizer’s Abrysvo is a bivalent RSV prefusion F (preF) vaccine that is composed of two preF proteins selected to optimize protection against RSV A and B strains. The FDA also approved Abrysvo to prevent RSV in infants.

Separately, the FDA approved Sanofi and AstraZeneca’s Beyfortus (nirsevimab-alip), which prevents RSV in newborns and infants. Beyfortus is the first monoclonal antibody to protect infants through their first RSV season. Although designed to prevent disease like a vaccine, it is not a vaccine because it does not stimulate the immune system.

The FDA also granted accelerated approval in November 2023 to Ixchiq, the first vaccine to prevent the mosquito-borne virus chikungunya. It was approved for use in adults age 18 and older. Infection with chikungunya virus can lead to severe disease and prolonged health problems, particularly for older adults and individuals with underlying medical conditions.

Ixchiq is administered as a single dose injected intramuscularly. Its manufacturer, Valneva, has begun a phase 2 trial of the vaccine in children one to seven years of age. Once available, the phase 2 pediatric data are intended to support a phase 3 pivotal study in children to extend the label. A clinical study in adolescents is also ongoing in Brazil.

2024 vaccine outlook

This year the FDA could approve additional vaccines, including the first self-administered flu vaccine. AstraZeneca has submitted a supplemental biologics license application for a self-administered option for FluMist Quadrivalent, which is a needle-free nasal spray. Researchers said this would provide another option for flu vaccination and potentially increase access and use of flu vaccine.

The FDA has set a Prescription Drug User Fee Act (PDUFDA) date for a regulatory decision during the first quarter of 2024. If approved, Astra Zeneca has said it will be available for the 2024-2025 flu season.

Regulators are also reviewing Merck’s Biologics License Application for a pneumococcal conjugate vaccine specifically designed to help prevent invasive pneumococcal disease and pneumococcal pneumonia in adults. The vaccine was developed using the serotypes responsible for about 80% of pneumococcal disease in those over age 65. The PDUFDA action date is June 17, 2024.

Even though advances have been made in the area of vaccines, the question remains whether Americans will accept and get these vaccines. Vaccine hesitancy, which ranges from misgiving to outright resistance, took hold during the COVID-19 pandemic because of misinformation about the COVID-19 vaccines, and it has shown staying power.

The proportion of U.S. adults who have received COVID-19 vaccines, flu and RSV remains low, according to recent data from the Centers for Disease Control and Prevention. Just 21.4% of adults over the age of 18 have received the COVD-19 vaccine, while 41.5% have gotten a flu vaccine.

Vaccine hesitancy is not just about COVID-19 vaccines. Cases of measles have surged in the Washington, D.C., area, Pennsylvania, New Jersey, Delaware and Washington state, partly because children have not been vaccinated.

In a recent study, researchers from the University of Colorado School of Medicine found that while the COVID-19 pandemic did not affect parent vaccine hesitancy overall, some misinformation about COVID-19 may be impacting parental trust in childhood vaccines.

A survey by researchers from the University of Michigan School of Public Health found that 12% of parents believe that childhood vaccines are less important compared with before the pandemic and that 13% believe that childhood vaccines are less effective now. They also found that negative beliefs about childhood vaccines were clustered in places with low COVID-19 vaccination rates.

In another study, researchers from the University of Colorado School of Medicine found that misinformation about COVID-19 may be impacting parental trust in childhood vaccines.

Vaccine Approvals in 2023

• Abrysvo to prevent respiratory syncytial virus (RSV) in older adults
• Arexvy to prevent RSV in older adults
• COVID-19 updated vaccines from Pfizer, Moderna, Novovax
• Cyfendus to prevent anthrax infection post exposure; it had been available through an emergency use authorization since 2019.
• Ixchiq first vaccine to prevent the mosquito-borne virus chikungunya virus
• Penbraya to prevent five strains of meningococcal infection in adolescents and young adults