With all the good news about vaccines now available for the Covid-19 virus, what will we worry about next? The answer is “How long will the vaccine immunity last?”

There is good news on that question from Massachusetts Institute of Technology (MIT). A new study shows Covid-19 patients who recovered from the disease still show robust immunity from the coronavirus eight months after infection. The authors of the study believe immunity to the virus probably will last for many years.

Neel V. Patel, writing in MIT Technology Review, says this should alleviate fears that the Covid-19 vaccine would require repeated booster shots to protect against the disease and finally get the pandemic under control.

“There was a lot of concern originally that this virus might not induce much memory,” says Shane Crotty, a researcher at the La Jolla Institute for Immunology in California and a coauthor of the new paper. “Instead, the immune memory looks quite good.” 

The study, published January 6 in Science, contrasts with earlier findings that suggested Covid-19 immunity could be short-lived. Many feared this would put millions who’ve already recovered from the virus still at risk. But the new study suggests reinfection should only be a problem for a very small percentage of people who’ve developed immunity – whether through an initial infection or by vaccination. The few individuals who fail to develop long-lasting immunity will be protected by the development of herd immunity in the larger population.

The study took blood samples from 185 men and women who had recovered from Covid-19. Each person provided at least one blood sample between six days and eight months after their initial symptoms, and 43 of the samples were taken after six months. They also measured the levels of several immunological agents that work together to prevent reinfection: antibodies, B Cells, and T Cells.

The researchers found that antibodies in the body declined moderately after eight months, although levels varied wildly between individuals. But T-Cell numbers declined only modestly, and B-Cell numbers held steady and sometimes inexplicably grew. That means that despite decreases in free-flowing antibodies, the components that can restart antibody production and coordinate an attack against the coronavirus stick around at pretty high levels. The same mechanism that leads to immune memory after infection also forms the basis for immunity after vaccination, so the same trends ought to hold for vaccinated people as well.

There is additional encouragement found in the study of people who have recovered from SARS, a close cousin of the virus that causes Covid-19. A study published in August showed that T-Cells specific to SARS can remain in the blood for at least 17 years, bolstering hopes that Covid-19 immunity could last for decades.

While this is only one study with a limited number of patients, it gives us all much encouragement that immunity from this Covid virus will last, possibly for years. This is great news and should be additional motivation for everyone to get vaccinated