After more than a year of lockdowns and mask wear, more than 63 million people have been completely vaccinated against COVID-19, marking an important milestone toward ending the pandemic.
Clinical studies have shown that the approved coronavirus vaccines are both safe and successful in avoiding serious COVID-19 infections. However, there is one question that researchers are still working to answer: how long does vaccine safety last? Will additional doses be needed to maintain immunity and protect against new, more contagious strains of the virus?
Data is still evolving, but it seems to be encouraging. Here's what experts have seen so far.
How Long Does COVID-19 Vaccine Immunity Last?
It's normal to wonder how long this defense will last for so many Americans being immunized - and millions more entering every day.
Pfizer reported on April 1 that its vaccine provides good defense against symptomatic COVID-19 for up to six months. The vaccine was 91.3 percent effective at avoiding COVID-19 for up to six months after the second dose, according to results from its phase 3 trial, and 100 percent effective against severe disease as described by the CDC.
According to the letter published in The New England Journal of Medicine on April 6, Moderna's vaccine provides equal defense so far. Researchers discovered that "antibody activation persisted high" six months after the second dose in both age ranges.
As part of their Phase 3 clinical trials, Los Angeles Times said the first two vaccines approved by the Food and Drug Administration - one made by Pfizer and BioNTech and the other by Moderna - began going into arms in late July. In the Pfizer-BioNTech experiment, the second dose was given three weeks later, and in the Moderna trial, it was given four weeks later.
It takes another two weeks for the immune system to work up to maximum defense after the second dose. That means the first individuals to be properly immunized reached this milestone in September, roughly six months ago.
Richard Watkins, M.D., an infectious disease physician and professor of internal medicine at Northeast Ohio Medical University, told Prevention.com that the findings are identical since both vaccines use mRNA technologies and therefore evoke the same immune response.
As a result, William Schaffner, M.D., an infectious disease physician and professor at Vanderbilt University School of Medicine, said six months is the period over which they have safe information."
However, researchers are also researching how effective the vaccines perform against new variants, but this does not mean the vaccines are only good for six months.
Hence the response is now is as unsatisfying as it is simple: no one knows now.
"We don't know yet how long immunity lasts from the vaccines that we have at hand right now," Dr. Katherine O'Brien, who heads the vaccines department at the World Health Organization, said in a podcast. "We're really going to have to wait for time to pass to see just how long these vaccines last."
The vaccine manufacturers are keeping track of these clinical trial participants and monitoring them to see if the results of their vaccinations have been consistent or have started to fade. Both seem to be in good shape so far.
In the meantime, both manufacturers are developing immune system booster shots to strengthen a weakened immune system. Some of the boosters are engineered to help target new coronavirus strains that have appeared since the first vaccines were created.
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