While many have raised questions and have concerns about the vaccine, one of the most common questions is will the vaccine be a one-time injection or will it require recurring vaccinations. According to a new study, Covid-19 patients who recovered from the disease have robust immunity from the coronavirus eight months after infection.
This is a positive sign that the authors interpret to mean immunity to the virus probably lasts for many years, and it should help remove fears that the covid-19 vaccine might require repeated booster shots to protect against the disease and work toward getting control of the pandemic.
“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 co-author of the new paper. “Instead, the immune memory looks quite good.”
Published January 6 in Science, a study contrasts with earlier findings that suggested that covid-19 immunity may be short-lived, causing millions who’ve already recovered to be at risk of reinfection.
Those findings should not have been a surprise, since infection by other coronaviruses has been known to generate antibodies that fade fairly quickly.
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 new study does in fact show that long-lasting immunity is not present in a small number of recovered people; however, the vaccination should offset that concern by ensuring herd immunity in the larger population.
The new paper studied blood samples from 185 men and women who had recovered from a mild infection of covid-19—although 7% were hospitalized. At least one blood sample was provided by each person between six days and eight months after their initial symptoms, with 43 of the samples taken after six months.
The team that ran the investigation measured the levels of several immunological agents that work together to prevent reinfection: T cells (which kill infected cells) antibodies (which tag a pathogen for destruction by the immune system or neutralize its activity), and B cells (which make antibodies).
Researchers found that antibodies in the body declined moderately after eight months, with levels varying greatly between individuals. T-cell numbers declined only modestly, and B-cell numbers held steady, but sometimes inexplicably multiplied.
This indicates that despite decreases in free-flowing antibodies, the components that can restart antibody production and coordinate an attack against the coronavirus stick around at very high levels.
Crotty adds that the same mechanisms that lead to immune memory after infection also form the basis for immunity after vaccination, hopefully, the same trends will hold for vaccinated people as well.
And while immunity to other coronaviruses has not proven noteworthy, it’s important to look at what happens in people who 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, which offers hope that covid-19 immunity could last for decades.
The new study is encouraging but not perfect. Perhaps it would have been beneficial to collect multiple blood samples from every participant for more data. “Immunity varies from person to person, and uncommon individuals with weak immune memory still may be susceptible to reinfection,” Crotty cautions.
It would be unwise and unprofessional to draw firm conclusions about covid-19 immunity until years have passed—it’s simply too soon. Nonetheless, this latest result is a good indication that if the vaccination rollout goes well (and that is a big if), we’ll be able to put the pandemic behind us very soon.