Vaccines should end the pandemic, despite the variants, say experts

By | March 1, 2021

A Harvard immunologist said current vaccines appear to be effective enough to end the pandemic, despite growing concerns that more infectious COVID-19 variants would severely blunt the effectiveness of the preventative treatments and set the nation back in its fight against the disease.

Galit Alter, professor of medicine at Harvard Medical School and the Ragon Institute of MGH, MIT, and Harvard, said the fast-spreading U.K. variant seems able to evade some vaccine protection, and the South African variant appears able to skirt even more. Despite that, she said, none have completely escaped the body’s post-vaccination immune responses.

That’s because, Alter said, though much attention has focused on how antibodies boosted after vaccination target their attack on the virus’ spike protein, the immune system has an array of other defenses that vaccination also mobilizes, including antibodies that attack other parts of the virus, and, importantly, T-cells that attack the infected cells the virus hijacks in order to replicate.

“What we’re seeing is that these variants don’t seem to affect T-cell immunity all that much and they [the T-cells] seem to be as effective in recognizing these variants as they do the original virus,” Alter said. “What that means is that we actually have very important backup mechanisms built into our vaccines that will continue to provide protection against these newly emerging variants.”

Alter, speaking during a noontime briefing Wednesday by the Massachusetts Consortium on Pathogen Readiness (MassCPR), said that even if our most effective vaccines’ effectiveness falls to 70 percent from 95 percent, the world still has a path to achieving the herd immunity that can end the pandemic.

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“What we see is that immunity conferred by the vaccine can essentially completely limit the breakout of any infections in the population,” Alter said. “These data give us hope that even with the vaccines that do not confer 95 percent protection against these emerging variants, the light at the end of the tunnel is approaching.”

That doesn’t mean the road ahead will be easy, Alter said. She acknowledged that the lower level of effectiveness against the variants means that more people will have to be vaccinated to achieve the same population-wide protective effects. Earlier estimates based on highly effective vaccines held that 50 percent to 60 percent of the population would have to be vaccinated in order to create herd effects. At 70 percent effectiveness, she said, the threshold will rise to roughly 75 percent, significantly higher, but nonetheless still achievable.

Health & Medicine – Harvard Gazette