A new study has found that some vaccines may offer COVID-19 immunity for years, especially for those who contracted and recovered from the virus before immunization.
In a study shared online by journal Nature on Monday, scientists reported that messenger RNA (mRNA) COVID vaccines, like those produced by drug companies Pfizer and Moderna, induced a persistent immune response in humans that indicate long-lasting immunity against the virus. (The study has been peer reviewed but not officially published, though an early version of it has been made available online).
Researchers specifically examined how the mRNA vaccines impacted humans’ memory cells, which are called “memory B cells.”
After a person is infected with a virus, or after they receive a vaccination for one, a structure called a germinal center forms in the lymph nodes. There, B cells learn all about the virus and are essentially trained to recognize and fight the virus if ever introduced again.
The scientists say that, largely based on research in animals, germinal center responses typically peak 1-2 weeks following infection or vaccination -- meaning the B cells are strengthening their knowledge for that period of time. This study found that after humans were given mRNA COVID vaccines, the B cells in the germinal center “maintained at or near peak frequencies for at least 12 weeks after secondary immunization.”
The highly active reaction was found in humans who had previously recovered from COVID, and then later received both doses of the Pfizer mRNA vaccine.
So, with more time at “peak” frequencies to learn about the virus, the B cells are even more prepared to recognize and combat COVID in the future. The scientists say that vaccinated individuals should essentially be immune to all existing virus variants for the foreseeable future.
The researchers that those who have not been infected but have been immunized likely won’t require any additional booster shots to fight against virus variants -- that is, unless variants transform significantly, which is possible. Those who have survived COVID and have been vaccinated for the virus may not need booster vaccines, period.
Still, existing COVID vaccines have proven to be largely effective against known variants circulating the world, though the delta variant has raised some concern.
Other research, led by some of the same team members, shows that immune cells that recognize and fight against COVID-19 lie dormant in bone marrow for at least eight months following infection.