Yes but
"but having having had covid" is really the key point.
For those of us who have not had it (or at least think we have not), surely the best course of action is to have had three doses so that when we do eventually catch Covid we are less likely to have a severe negative outcome.
And if it was a choice to deliberately catch Covid I would much rather do so after my third dose.
Effectiveness wanes over time, but protection against critical illness can persist longer
www.aarp.org
B cells and T cells: It’s not all about the antibodies
Neutralizing antibodies, though commonly discussed, is only one key component in this defense. These germ-attacking proteins spike after vaccination or infection (both trigger their production) and circulate in the blood, keeping an eye out for the virus. If they recognize an invader, they’ll attempt to bind to the virus, interfering with its ability to infect the cells. However, omicron has complicated their efforts: According to the National Institutes of Health, antibodies generated by the COVID-19 vaccines “don’t recognize their targets as well in heavily mutated variants like omicron,” which helps to explain why we’ve seen so many breakthrough infections since the variant rose to dominance.
What’s more, research suggests these neutralizing antibodies lose steam over time, and their levels drop off after several months.
That’s where the next line of defense comes in: specifically, B cells, which make the antibodies, and T cells, which patrol and destroy the cells infected with the virus.
“You can imagine that the B cells are soldiers that shoot out bullets, and the bullets are the antibodies. So once the attacker is gone, the soldiers stop shooting. It would be a waste of ammunition to keep on making antibodies for a virus that is no longer there,” Sette explains. If the virus comes back, “they are ready to go in a matter of days to mount a full-blown immune response again,” Sette says.
A new preprint study, first reported on by The New York Times, found that a third dose of an mRNA vaccine (Pfizer or Moderna) increases the power of these B cells, allowing them to “produce antibodies capable of clearing even diversified variants such as omicron” within a few days of recognizing an invader, the report’s authors note. This can help explain why a booster shot of an mRNA vaccine that was not “specifically designed to protect against variants is effective against variant-induced serious disease,” they write. The research, however, has not yet been peer reviewed.
“The B cells have this amazing capacity of continuing to evolve,” Sette explains, adding that even in the absence of an ongoing infection, “you have this continued maturation of the antibody response.”
What’s more, research from Sette and others shows that the majority of T cells — these are the cells that help to control and terminate an infection — generated after vaccination continue to recognize coronavirus variants, including omicron. “These cells won’t stop you from getting infected, but in many cases, they are likely to keep you from getting very ill,” Shane Crotty, a professor at La Jolla Institute for Immunology and a coauthor of the study published in Cell, said in a statement. (The data from the study stemmed from fully vaccinated, but not yet boosted, adults. The researchers are currently studying T cell responses in boosted individuals.)
It’s not clear how long these responses last, but B and T cell responses tend to persist for some time, experts say. According to Sette, T cells lasted more than a decade after infection with the SARS virus that was behind the 2003 outbreak in Asia.