By Maayan Hofmann
Health experts have expressed reservations about the safety and efficacy of a fourth COVID vaccine dose, even as half a million Israelis have taken the extra jab.
A health worker prepares a fourth dose of Pfizer COVID-19 vaccine at the Sheba Medical Center, Dec. 31, 2021. (Tomer Neuberg/Flash90)
“I don’t know if there’s a need for a fourth booster,” said Pfizer CEO Albert Bourla during a recent interview with American media.
“That’s something that needs to be tested. . . . I don’t think we should do anything that isn’t needed.”
Last month, Israel became the first country in the world to administer fourth shots to the immunocompromised, the elderly and health care workers.
Last week, Greece approved a fourth shot for those at highest risk.
Chile also announced that it would offer citizens a fourth vaccine dose, also starting with those who are at the highest risk of infection or developing severe disease, but those shots are not expected to begin until February and will be given only after six months have passed from the previous jab.
Brazil also has approved a fourth shot, but only for the immunocompromised.
Will the second booster be a lifesaver or a liability? The answer, it seems, is still unknown.
A representative of the European Medicines Agency expressed reservations last week, warning that too frequent COVID-19 vaccination could harm immune response.
Boosters “can be done once, or maybe twice, but it’s not something that we can think should be repeated constantly,” Marco Cavaleri, EMA’s head of biological health threats and vaccines strategy, said at a press briefing.
“While the use of additional boosters can be part of contingency plans, repeated vaccinations within short intervals would not represent a sustainable long-term strategy.”
The World Health Organization also put out statements against a widespread fourth dose — though the organization has acknowledged the necessity of a third shot in some cases.
“With near- and medium-term supply of the available vaccines, the need for equity in access to vaccines across countries to achieve global public health goals . . . a vaccination strategy based on repeated booster doses of the original vaccine composition is unlikely to be appropriate or sustainable,” the WHO said on Jan. 11.
“While some countries may recommend booster doses of vaccine, the immediate priority for the world is accelerating access to the primary vaccination.”
Israeli researchers said they are not convinced that four doses will overload the immune system, though they did admit that a COVID policy based almost entirely on shots is proving ineffective.
Israel has been diagnosing more than 40,000 new cases per day for the last several days and experts believe the actual number of infected people is two to three times higher.
“You can get two booster shots, but to base your strategy on injections every four months — it does not make sense,” said Prof. Cyrille Cohen, head of the immunology lab at Bar-Ilan University.
“We have a problem, and we have to recognize there is a problem and we have to solve it.
“Repetitive injections defeat the purpose of the vaccine, which is to stop severe infection. You cannot take a new dose every time you have a new variant.”
Israel’s decision to administer a fourth dose was “based on expert opinion and not robust data, because there was no robust data,” said Prof. Eyal Leshem, director of the Center for Travel Medicine and Tropical Diseases at Sheba Medical Center.
His hospital has been at the forefront of evaluating the effectiveness — and waning — of the Pfizer coronavirus vaccine.
The hospital is in the midst of a clinical trial evaluating the safety and effectiveness of a fourth dose of both the Pfizer and Moderna vaccines on around 300 healthcare workers.
Sheba released preliminary results showing that the extra booster is safe in the short term and leads to a fivefold increase in antibodies.
However, the trial’s lead researcher, Dr. Gili Regev-Yochay, told Army Radio that “the amount of antibodies returns to the level it was after the third vaccine, not more. It’s nice, but it’s not what we expect from a booster.”
Leshem also said that that there are multiple vaccines for which people receive three or more doses, including the polio vaccine that requires six doses over a lifetime. He admitted, however, that there are no vaccines that require so many doses in such a brief period.
“We do not have enough data to comment on whether the decision to give a booster provided enhanced protection against severe disease or hospitalization.”
To assess the actual benefit of the booster, Leshem said, scientists will have to compare all the people susceptible to severe disease that received a fourth dose to those who could have but did not — something which will only be able to be done effectively in several weeks.
Meanwhile, “I don’t think it will harm anyone.”
For now, Israel has stuck to only administering the vaccine to those facing the highest risk from infection.
At the same time, research is showing that while vaccine effectiveness will be reduced against symptomatic disease caused by the Omicron variant, protection against severe disease is more likely to be preserved, according to WHO.
More than 60% of Israelis have received two doses of the coronavirus vaccine, around 80% of the eligible population has received two doses and a booster jab. Almost 25% of children aged 5-11 have also been jabbed since Israel opened its kids’ vaccination campaign in November.
Vaccination, both Leshem and Cohen said, are likely part of the reason that while severe cases are rising, they are doing so at a much slower pace than in any previous waves, though it is understood that the Omicron variant in general is less virulent than previous variants.
Data provided by the Health Ministry shows that there is an almost tenfold reduction in severe disease among people over the age of 60 who are fully vaccinated compared to those who are not.
Leshem said that as more vaccinated Israelis catch Omicron, the combination with immunity may prove most effective and alleviate the need for any future booster.
