It’s still too early to tell — but experts are getting closer to cracking the code.
“We’ll have to see where this all interacts. Is it possible we’re going to need a booster at some point? Yes. Is it probable? Yes. Do we know exactly when? No,” Marks said. “But if I had to look at my crystal ball, it’s probably not sooner, hopefully, than a year after being vaccinated, for the average adult.”
And, experts emphasize, anyone who is fully vaccinated currently should still be protected. But the reason why the timeline for potential boosters remains unclear is because scientists still need time to collect the data on how long immunity against Covid-19 may last in the future — and how to factor in future variants.
And even if someone recovered from a previous infection and has a natural immunity, vaccinations can help give their immune memory a boost.
Vaccine makers monitoring immunity
Currently, three coronavirus vaccines are authorized for emergency use in the United States: the two-dose Pfizer/BioNTech vaccine for ages 12 and older; the two-dose Moderna vaccine for ages 18 and older; and the single-dose Johnson & Johnson vaccine for ages 18 and older.
All three companies are investigating the potential use of boosters.
Vaccine makers have been studying whether the immunity these vaccines elicit may wane over long periods of time — say, possibly, after a year or more — and whether they protect as well against coronavirus variants that could emerge and evolve.
If so, a vaccinated person might need a booster dose of vaccine to stay protected against the original coronavirus strain and newly emerging variants — somewhat similar to how a tetanus booster is recommended every 10 years, or different flu vaccines are recommended each year.
Still, doctors are worried that coronavirus may end up being like influenza, which requires a new vaccine every year both because the circulating strains mutate fast, and because immunity from the vaccine wears off quickly.
“Thus, cellular immunity may help limit disease severity in infections caused by variants that partially escape neutralizing antibodies,” according to the CDC.
Immunity could last much longer; researchers just need the time to evaluate.
That degree could be measured as whether people who are fully vaccinated eventually have breakthrough infections at a higher rate, or have infections that are severe enough to require hospitalization.
“To me, that is the threshold,” Adalja said.
Meanwhile, studies into natural immunity from being previously infected with the coronavirus have been ongoing for somewhat longer than vaccine trials.
The latest findings on a long-lasting immunity
Two new studies this week add to the growing body of evidence that suggests natural immunity to the coronavirus after someone recovers from Covid-19 can be long lasting — possibly at least a year. But that doesn’t mean they shouldn’t get vaccinated. It also doesn’t mean immunity will last forever.
Bone marrow cells may maintain a memory of Covid-19 for at least 11 months after someone is infected. These cells are an “essential” source of protective antibodies, according to the new study published in Nature.
Researchers from Washington University in St. Louis examined blood samples from 77 people previously infected with SARS-CoV-2, the virus that causes Covid-19. The researchers found an initial decrease in the presence of Covid-19 antibodies after infection, but between four and 11 months the decline slowed.
The researchers also examined bone marrow samples taken from 19 previously infected patients, about seven and 11 months after infection. The researchers found Covid-19 antibodies in 15 of the 19 patients — and unlike the decline in other antibodies observed, those produced by cells in the bone marrows appeared to remain stable.
But he added that the findings do not suggest that people who have had Covid-19 no longer need to get vaccinated. Rather, vaccination could enhance the natural immune response even more.
“I think people who had been infected and produce this beautiful memory over time, it would be a great incentive to get the vaccine because now you can put these memory cells into action,” Ellebedy said, adding that having antibodies does not mean a person is completely protected.
“Our data explains why those who experienced mild SARS-CoV-2 infection in the last year are generating such awesome responses to vaccination. It is because of the robust immune memory that they developed after infection,” Ellebedy told CNN in an email on Thursday.
“However, not all previously infected people are the same,” he added. “For many different reasons, some individuals do not generate a robust immune response to infection even after surviving infection. So it is best that they get both vaccinations,” for those receiving a two-dose vaccine.
For those same reasons — whether it be due to age or being immunocompromised — some people might be recommended to follow a different booster schedule than others in the future, if booster shots are eventually needed.
As many as 9 in 10 people infected with the coronavirus develop natural immunity against the virus that is “sustained with little decay” up to 10 months after their initial infection, suggests the EClinicalMedicine study, conducted by researchers at the national clinical laboratory Labcorp.
The researchers found that about 90% recovered Covid-19 patients tested in the study had detectable antibodies by 21 days following infection — and antibody rates remained around 90%, given some variability, up to 300 days.
The researchers analyzed data on 39,086 people who were confirmed to have Covid-19 between March 2020 and January 2021, and had at least one antibody test performed with Labcorp after testing positive for the coronavirus infection.
The data did not include patients’ demographic information or information about how severe a particular Covid-19 case was.
CNN’s Maggie Fox, Ryan Prior and Naomi Thomas contributed to this report.Source link