Experts: COVID boosters for at-risk groups may help avert new variants

As the world worries about the prospect of new coronavirus variants, Israel’s booster shot policy may help to address an important vulnerability.

Jerusalem blazed a trail two weeks ago, announcing that most immunocompromised people could receive a third shot of Pfizer’s coronavirus vaccine.

Only France had such a policy before Israel, and only a few other countries have followed so far. As the immunocompromised have started heading to clinics, coverage has focused on the protection it would give to this at-risk population.

But boosters to this limited sector of the population could actually help to address a vulnerability faced by all, according to Dr. Oren Kobileer, a variants expert from Tel Aviv University’s school of clinical microbiology and immunology.

“It’s believed that new variants arise when immunocompromised people are infected,” Kobileer tells The Times of Israel. This happens because the virus stays in such people’s bodies for longer than normal, creating conditions under which it is prone to mutation.

Bolster the protection for the immunocompromised and you reduce the chance that a cancer patient, transplant recipient, or someone else with a weakened immune system will give rise to a new variant, said Kobileer.

Prof. Tomer Hertz, computational immunologist from Ben Gurion University, agrees.

“As it’s likely that most variants have arisen in immunocompromised individuals, if the booster successfully increases their antibodies, it will reduce the chance of variants,” he says.

This could help reduce the risk of the emergence of a new Israeli variant, which like all new variants could turn out to be more contagious, more vaccine-proof, or more harmful to the body. And given that local variants can spread particularly fast in the countries where they arise, limiting the prospects of a local variant is valuable, says Hertz.

Illustrative: A chemotherapy patient in a hospital. (iStock via Getty Images)

The logic of boosters for the immunocompromised could really make a difference in the global fight against variants if they are proven to work and other countries follow the lead of Israel and France, Hertz believes.

He thinks that over the coming weeks, officials around the world will look to Israel and France to get data to guide this discussion: namely whether boosters are succeeding in protecting those at-risk, and if so, what is the extent of the added protection.

It’s still far from certain that boosters will be shown to increase protection of the immunocompromised: the very nature of the challenge is that their immune system doesn’t respond as well to vaccines as those of the general population.

But Kobileer is optimistic.

A man receives a booster dose of the coronavirus vaccine at Sheba Medical Center outside of Tel Aviv, on July 12, 2021. (Courtesy Sheba Medical Center)

Given that vaccines both prevent infection and increase the ability to fight the coronavirus if infected, he thinks that boosters will reduce the chance of immunocompromised people catching the coronavirus and getting stuck in a “lingering” phase, during which they aren’t seriously ill but can’t shake the virus.

“The problem is when immunocompromised people aren’t very sick but nevertheless keep replicating the virus and have a high virus count,” Kobileer says. “The lingering of the virus is the problem.”

“With the boosters, we are reducing the chances of it lingering,” he adds. “And the logic would suggest that when you reduce the chances of this lingering effect, you reduce the chances of a new variant arising.”

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