As Israel begins rolling out fourth COVID-19 vaccine doses and other nations push booster shots amid the spread of the highly contagious Omicron variant, some US health experts are questioning whether “forever-boosting” is an effective long-term strategy for dealing with the coronavirus.
Speaking with The New York Times, the scientists said periodically offering booster shots to entire populations does not appear viable, nor make sense scientifically.
“This doesn’t seem to be a sustainable long-term strategy, for sure,” Deepta Bhattacharya, an immunologist at the University of Arizona, told the newspaper.
Beyond the medical effectiveness, they cited likely public vaccination fatigue, noting that while around 73 percent of adults in the United States have received two vaccine shots, only a third so far have gotten a booster. In Israel, which first began administering booster shots over the summer, nearly 6 million people have received at least two doses, while far fewer — over 4.3 million — have gotten a third.
“It’s not unheard of to give vaccines periodically, but I think there are better ways than doing boosters every six months,” Akiko Iwasaki, an immunologist at Yale University, was quoted as saying, adding that there were other approaches to “get us out of this forever-boosting kind of a situation.”
Among the potential alternatives mentioned in the report were a vaccine specifically targetting the Omicron variant, a “pan-coronavirus vaccine” that targets parts of the virus that do not evolve; combining the current shots with nasal or oral vaccines that help better prevent infection by blocking the virus from entering the body; and waiting longer periods between administering doses.
While backing a third shot for Americans, the experts said increased antibody levels are not a guarantee against infection from Omicron, and that the immunity boosters provide may be transient.
“Even with that amount of antibody, it’s very hard to stop the virus for very long,” said virologist Shane Crotty of the La Jolla Institute for Immunology in California.
Crotty said a shot tailored to Omicron could “do a better job” against the virus, which several of the major vaccine manufactures have begun developing. Ali Ellebedy, an immunologist at Washington University in St. Louis, echoed Crotty.
“It doesn’t make sense to keep boosting against a strain that’s already gone,” Ellebedy said. “If you are going to add one more dose after three, I would definitely wait for an Omicron-based one.”
Scientists also said that there is more benefit to ensuring that most of the world gets vaccinated, which would slow the emergence of variants, as opposed to rich nations offering additional boosters.
Scott Hensley, an immunologist at the University of Pennsylvania, said the emergence of Omicron changed his position on boosters, but that there was little reason to follow Israel in offering fourth doses because other immune cells remained effective against the virus after three or even two shots.
Another immunologist said vaccines were succeeding in reducing serious morbidity and hospitalizations, and that Omicron showed trying to prevent infection altogether was not possible.
“People that are vaccinated really are doing very well in terms of hospitalization,” said Michel Nussenzweig of the Rockefeller University in New York.
The report also noted that there is not yet data on whether fourth vaccine doses are effective.
On Wednesday, Prime Minister Naftali Bennett said the fourth Pfizer vaccine shot causes a significant boost in antibodies within a week after taking it, citing interim data from Israel’s landmark study on the matter.
However, since the trial at Sheba Medical Center began just a week earlier, there is no data on whether the number of antibodies maintains itself over time after the first week, or whether the antibodies provide better protection against catching — or developing serious illness from — the Omicron variant, which has shown an ability to break through other vaccine defenses.
Bennett, who has pushed ahead with expanding Israel’s fourth dose program despite the lack of data, claimed that the fourth dose “expresses a much better protection than without that shot, both regarding infection and regarding serious illness.”
“The fourth vaccine is safe, that is certain. The fourth vaccine very likely works,” he added.
Sheba’s trial program, which began with 150 medical staff being given the shot, is many times smaller than normal drug trials, which usually involve thousands of volunteers who results are tracked for months. But it is also the only known study of the effects of a fourth dose, with Israel pinning hopes that the extra booster may help keep the variant from overwhelming hospitals and shutting down normal life.
National coronavirus czar Salman Zarka admitted Monday that little is known about the fourth dose, but urged those eligible to get it anyway.
“We’ve seen that the amount of antibodies is always dropping and so recommend that you, 60-and-overs and medical staff, get the fourth dose,” he said at a press conference. “I’ll say transparently, the data we have on a fourth shot is limited. Many experts think it provides extra protection to populations at risk.”
Zarka later told the Kan broadcaster that it was too early to discuss making the fourth shot available to others as well, but predicted it would be discussed in the near future.
Along with people over 60 and medical workers, Israel is also offering fourth doses to the immunocompromised.