While the world tussles with the Omicron variant, Israel has made plans to roll out fourth coronavirus vaccine doses for vulnerable parts of its population.
Israel, a leader in the global inoculation effort, said Tuesday that it hopes to administer additional shots to medical workers and people over 60, at least four months after they receive the third dose of an mRNA vaccine. It could further bolster immunity among the Israeli population — more than 90 percent of whom are fully vaccinated, largely with the Pfizer/BioNTech regimen of two shots plus a booster.
The announcement begs the question: Could a fourth dose be in the cards for the US? And could its arrival quell yet another surge of cases down the road?
Maybe not, said Dr. Paul Offit, the director of vaccine education at the Children’s Hospital of Philadelphia and a member of the Food & Drug Administration advisory panel on vaccines.
A fourth shot could help inoculated Americans temporarily fend off mild cases of the virus by increasing their antibody levels, he said. But the biological defenses in the initial two vaccine doses are what allow the body to fight severe illness, hospitalization, and death. (Preliminary research shows that the Moderna and Pfizer vaccines provide roughly 70 percent protection from Omicron, and higher levels against earlier strains.)
Instead, Offit said, the answer to stopping hospitalizations and deaths lies in vaccinating the vast percentage of Americans who have refused shots.
“Further protecting the already protected [with fourth doses] is not the problem,” he added. “The problem is figuring out a way to protect the unvaccinated ... They’re the ones who are getting seriously ill. They’re the ones who are coming to the hospital. They’re the ones who are dying and spreading this virus.”
But Offit said fourth doses may have a positive impact in highly vaccinated countries like Israel. There, authorizing additional booster doses could lower the number of total infections sparked by Omicron and any future variants.
At least, that’s what Israeli experts hope.
Health officials believe the distribution of third doses helped bring down the country’s August and September wave.
Still, professor Galia Rahav, a member of the expert panel that recommended the fourth dose in Israel, said on Israeli radio that scientists have little data on what level of immunity the fourth shot will provide. But “in a situation like this, if you don’t act immediately, you miss the train,” she added.
The number of Omicron cases in Israel doubled on Tuesday to 340, according to its health ministry, with the total number of cases rising to a two-month high of 1,306.
But in the US, Americans have been slow to take to a third dose — let alone a fourth one. Of American adults eligible for a booster shot, only about 30 percent have received one, according to the Centers for Disease Control and Prevention last week. In all, just 1 in 6 US residents has received a booster.
Dr. Shira Doron, an infectious disease physician and epidemiologist at Tufts Medical Center, said releasing additional vaccines doses in the US is a less feasible strategy for that reason.
“I don’t think we can keep vaccinating people every couple months,” she added. “People will accept it less and less in this country because of how much mistrust there is and how hard it has been to get people to act in the first place.”
Now, Doron said, the US needs to nail down a goal for what the vaccine can — and can’t — do. “Is it to help with mild illness or severe illness?”
Regardless, the timeline with which fourth doses would be distributed in any country outside Israel remains unclear.
Rajat Desikan, a principal scientist at the New Jersey-based biosimulation and drug discovery company Certara, wrote in an e-mail that “it is reasonable for people to expect a fourth dose in 2022, if they have received a booster this year.” It’s all dependent, he added, on the rate and severity of new variants and how fast they spread.
Offit contends that no matter which path the US takes, COVID is here to stay.
“At some point, we’re going to get comfortable with the fact that there are people who are mildly ill with this virus,” he said, “in the way that we’re comfortable with the fact that there are people who are mildly ill with the flu.”
Diti Kohli can be reached at diti.kohli@globe.com. Follow her @ditikohli_.