Now that 45 million Americans have been vaccinated from COVID-19/SARS-CoV-2, many are wondering how long the vaccines will last and if people will need to get annual shots like the flu shot every year. There is not enough information available to make any certain determinations, and contrary to a good deal of news reports, the FDA has approved none of the vaccines available in the United States; it has only authorized them for emergency use (EUA). The first dose of the mRNA vaccines (like those from Moderna and Pfizer-BioNTech) trains the immune system to recognize and attack the spike protein on the surface of SARS-CoV-2, the virus that causes COVID-19.
For example, the Moderna mRNA-1273 vaccine starts off at 94 percent effective against COVID-19, and it will begin denigrating its effectiveness 119 days (three months) after getting the vaccine for those over 56 years of age according to one small study published in the New England Journal of Medicine. For those 55 and under, the vaccine efficacy will last longer; however, much more study is needed for conclusive results. We do not know enough about the Pfizer-BioNTech, Johnson & Johnson, or Janssen COVID-19 vaccines to rate their efficacy months after getting the shot, and studies are continuing to get the data needed to know how long the efficacy lasts. The only way to accurately compare the effectiveness of these COVID-19 vaccines is by direct comparison in head-to-head clinical trials, which has not occurred for these vaccines. The clinical trials for these vaccines occurred in different geographic regions and at different points in time. All the COVID-19 vaccines that the FDA has authorized for emergency use are at least 50% more effective than placebo in preventing COVID-19 at the time they are given.
According to research from the National Institutes of Health, those who have already had COVID-19/SARS-CoV-2 will have natural immunity up to eight months of infection. Antibodies—proteins that circulate in the blood—recognize foreign substances like viruses and neutralize them. The researchers found durable immune responses in the majority of people studied. Antibodies against the spike protein of SARS-CoV-2, which the virus uses to get inside cells, were found in 98% of participants one month after symptom onset. As seen in previous studies, the number of antibodies ranged widely between individuals. But, promisingly, their levels remained fairly stable over time, declining only modestly at 6 to 8 months after infection. This study’s results were further supported with a much larger study out of England with healthcare workers who had contracted the virus and had immunity for many months after. All studies have shown a slow decline in natural immunity after eight months, and it is unknown how long it takes an average human to no longer have that immunity.