Updated COVID-19 vaccines effective against variants, new data show
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Key takeaways:
- Updated COVID-19 vaccines were 54% effective against symptomatic SARS-CoV-2 infection.
- The vaccines protected against the currently dominant JN.1 viral lineage, but protection wanes over time.
The updated COVID-19 vaccines were approximately 54% effective against symptomatic SARS-CoV-2 infection and offered protection against JN.1 and XBB viral lineages, according to early estimates published Thursday by the CDC.
The monovalent vaccines, which replaced previous bivalent vaccines this past fall, target SARS-CoV-2 omicron XBB virus lineages. XBB lineages were predominant in the United States until December, when JN.1 lineages surpassed XBB. JN.1 made up roughly 86% of circulating SARS-CoV-2 viruses in the U.S. as of Jan. 20.
Although Pfizer and Moderna reported that the updated vaccines were effective against newly emerging strains, members of the CDC committee that recommended them raised concerns about a lack of data on their efficacy against XBB.
“Whereas the goal of the U.S. COVID-19 vaccination program is to prevent severe disease, vaccine effectiveness (VE) against symptomatic infection can provide useful insights into protection early after introduction of updated vaccines and during the emergence of new lineages, such as JN.1,” CDC epidemiologist Ruth Link-Gelles, PhD, and colleagues wrote in the new study.
Link-Gelles and colleagues analyzed data on 9,222 adults who were tested for SARS-CoV-2 infection as part of the CDC’s Increasing Community Access to testing at a CVS or Walgreens pharmacy between Sept. 21, 2023, and Jan. 14, 2024. Among the tests included in the analysis, case-patients were those who received a positive nucleic acid amplification test (NAAT) and control patients were those who received a negative NAAT.
Among the 9,222 people who reported at least one potential symptom of COVID-19, 3,295 (36%) tested positive for SARS-CoV-2. Participants who tested negative were more likely to report having received an updated vaccine than people who tested positive, 14% vs. 9%.
Among the roughly 8,000 people who said they had not received an updated vaccine, 30% were unvaccinated. Among the remaining participants who had previously received a vaccine, 70% had not had an additional vaccine dose in at least 1 year.
Overall, VE was 54% (95% CI, 46%-60%) among people who had recently received an updated COVID-19 vaccine. The researchers found that VE for people aged 18 to 49 years was 57% (95% CI, 48%-65%) and for people aged 50 years and older was 46% (95% CI, 31%-58%).
Additionally, VE was 58% (95% CI, 48%-65%) among people tested for COVID-19 between 7 to 59 days after receiving an updated vaccine. It was 49% (95% CI, 36%-58%) among people tested for COVID-19 between 60 to 119 days after receiving an updated vaccine.
“Updated COVID-19 vaccines provide protection against symptomatic infection, including against currently circulating lineages,” Link-Gelles and colleagues wrote. “CDC will continue monitoring VE, including for expected waning and against severe disease.”
References:
- Link-Gelles R, et al. MMWR Morb Mortal Wkly Rep. 2024;doi:10.15585/mmwr.mm7304a2.
- CDC. COVID data tracker: Variant proportions. https://covid.cdc.gov/covid-data-tracker/#variant-proportions. Updated Feb. 1, 2024. Accessed Feb. 1, 2024.
Perspective
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With the advent of the omicron variant and, before that, other variants, vaccine effectiveness against symptomatic infection is less important because the vaccine’s value is chiefly premised on decreasing severe disease. Therefore, I think it’s better to think of these vaccines as having a transient and limited ability to block symptomatic infection, but a great ability to block severe disease in those who have a risk for severe disease.
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