Getting an updated dose will serve two purposes: protecting the individuals who are vaccinated, and also protecting the communities in which they live by creating a wall of immunity that reduces the risk that the virus can spread from person to person. But it’s reasonable to assume that they might, given that SARS-CoV-2 is also a respiratory virus that targets the lungs. Public health experts expect that COVID-19 cases will continue to ebb and flow around the world, and it’s not clear yet whether infections will peak during classic respiratory virus seasons like the flu and colds do.
“The situation for COVID-19 will be very similar…we need to get into a cycle or loop to get a new dose to boost protection.” “We know we get an influenza shot every year because the protection from last year’s shot doesn’t work through this year,” he says. In fact, says Ajelli, the flu vaccine and its immunization schedule could serve as a useful model for determining when COVID-19 vaccines should be given to keep protection as robust as possible. “That’s exactly in line with what we observe for influenza.” “This study is showing that the protection is very high at the beginning, but it wanes quickly,” says Marco Ajelli, associate professor of epidemiology and biostatistics at the Indiana University School of Public Health and one of the co-authors of the study. The studies in the review did not delve into how well the vaccines protect against more severe disease, hospitalizations, and deaths due to COVID-19 other studies to date have shown that protection against more serious outcomes wanes much more slowly than against symptomatic infection, and that the shots continue to protect pretty well against these more dire events. This drop in efficacy corresponded to rates of lab-confirmed positive tests for Delta and Omicron infections.
MODERNA VACCINE SECOND DOSE TIMING SERIES
This waning was greater during the Omicron wave than during the Delta wave, suggesting that the vaccine was less effective against Omicron.īooster doses after the primary series restored protection back to levels achieved just after the primary vaccination, but this protection waned too, at a rate similar to that after the primary series, dropping from 60% at one month after the booster dose to 13% at nine months.
(There were differences among the vaccines, with Moderna’s primary series of two shots showing the highest effectiveness of 62% one month after the series, and Sinovac’s demonstrating the lowest effectiveness at 32%.) After six months, the overall effectiveness of the vaccines dropped further to 14%, and to 9% after nine months. Overall, the researchers found that one month after people received two doses of either mRNA vaccine (from Moderna or Pfizer-BioNTech), the vaccine from AstraZeneca, or the shot from Sinovac, the vaccine effectiveness was 53% in protecting against symptoms of COVID-19.
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