“A year ago I tried the Moderna vaccine to see if it was safe. (Spoiler: It is!) Now, on my #COVIDvaccine anniversary, I’m happy to share that I just got a 3rd dose. This booster experiment will reveal (1) if strain-adapted vaccines boost immunity & (2) whether they are safe,” Haydon, a communications specialist at the University of Washington, said via Twitter last Saturday.
“It’s unclear whether this new tweaked version is even going to be necessary,” Haydon told CNN in a telephone interview.
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.
“It is still matched enough that we have good protection,” said Scott Hensley, an immunologist and vaccine expert at the University of Pennsylvania.
But vaccine makers are not taking chances. The trial Haydon is taking part in is testing not only a third dose of Moderna vaccine tweaked to protect specifically against B.1.351 — that’s what he got — but a third dose of original vaccine in some volunteers, too, to see if the boosted immune response is both safe and provides an advantage.
A report out last month from Pfizer suggests people who get both doses keep strong immunity for at least six months. Experts have been at pains to point out that doesn’t mean immunity stops at six months. It means that’s the longest volunteers in the trials have been followed to see what their immunity is. It’s likely to last much longer, Hensley said.
“I would not be surprised if we learned a year from now that these vaccines are still producing a strong immune response,” Hensley told CNN.
“I would not be surprised if this is a vaccine that we only get once.”
That would make the vaccine more akin to vaccines against measles than flu vaccines. Vaccination against measles protects against infection for life in 96% of people.
Protection from Pfizer’s two-dose vaccine remains above 91% even at six months, according to the company. It has released the details in a statement, not a formal scientific publication, and the data covers only a few thousand people. But if it holds up, that’s an indication that both the Pfizer and Moderna vaccines elicit a long-lasting immune response, experts say.
Hensley says the technology used by both vaccines — delivery of genetic…
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