COVID-19 immunity is temporary after vaccination or infection. Researchers examined long shot protection studies in a May 3 JAMA Network Open study.
The Italian-led researchers examined 40 studies on COVID-19 vaccination status and lab-confirmed infections. Both the Delta and Omicron surges were analyzed in the studies.
Protection Against COVID-19 Symptoms After Two Doses
One month after receiving two doses of the mRNA vaccine from Moderna or Pfizer-BioNTech, the vaccine from AstraZeneca, or the injection from Sinovac, 53% of individuals were protected against COVID-19 symptoms, according to the findings of the researchers.
There were differences between the vaccines, with Moderna’s primary series of two shots demonstrating the greatest effectiveness at 62% one month after the series and Sinovac’s vaccine demonstrating the least effectiveness at 32%.
After six months, the overall efficacy of the vaccines fell to 14%, and to 9% after six months. This warning was greater during the Omicron wave than the Delta wave, suggesting that the vaccine was less effective against Omicron.
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Targeting Strains for Vaccine Success
Booster doses administered after the primary vaccination series restored protection to levels attained immediately after the primary vaccination, but this protection also waned at a similar rate to that after the primary vaccination series, falling from 60% one month after the booster dose to 13% nine months later. This decrease in efficacy corresponded with lab-confirmed positive test rates for Delta and Omicron infections.
The studies in the review did not examine how well the vaccines protect against more severe diseases, hospitalizations, and deaths due to COVID-19; however, other studies to date have shown that protection against more serious outcomes wanes much more slowly than protection against symptomatic infection and that the vaccinations continue to protect fairly well against these more dire outcomes.
Experts in public health anticipate that COVID-19 cases will continue to fluctuate globally, and it is currently unclear whether infections will peak during traditional respiratory virus seasons, such as flu and cold seasons. Given that SARS-CoV-2 is also a lung-targeting respiratory virus, it is reasonable to assume that they do.
Like the annual flu shot, a COVID-19 vaccine must target the virus’s predominant strain. As with the annual flu vaccine, this requires some educated conjecture and some educated guesswork.
The U.S. Food and Drug Administration will convene a panel of vaccine experts in June to answer this question; this is the first step toward transforming COVID-19 into an updated and routinely administered vaccine.
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