The fourth Pfizer vaccine shot causes a significant boost in antibodies within a week after taking it, according to interim data from Israel’s landmark study on the matter made public Tuesday by Prime Minister Naftali Bennett.
Bennett heard the partial results during a tour of Sheba Medical Center near Tel Aviv, telling reporters that a week after receiving the fourth dose, recipients had almost five times more COVID-19 antibodies in their blood.
However, since the trial 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, noting that over 20,000 have received the additional booster and 100,000 more have ordered it since it was made available this week to Israelis 60 and older and medical workers.
Israel had already begun offering fourth vaccine shots to the immunocompromised last week.
The roll out of the extra booster shots comes as new daily cases surge, with Israel pinning its hopes on beating back an expected Omicron-driven wave by giving an extra boost of vaccine protection to its most at risk populations.
Sheba’s trial program, which began last week 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.
The World Health Organization has urged countries to delay booster programs until the whole world has access to initial vaccine doses. On Monday, Maria Van Kerkhove, the WHO’s technical lead on COVID-19, criticized the Israeli rollout.
“We will not be able to boost our way out of this pandemic. We need to increase vaccination among those most at risk in every single country and not just boost some people in some countries over and over again,” Van Kerkhove told the BBC.
Sheba’s Prof. Galia Rahav, who is running the trial at the hospital, pushed back when asked if Israel was moving ahead too quickly with the additional boosters.
“Look, we’re always ahead of the rest. That’s been the case the whole way. We learned a lot about the third shot before the rest. And we saw it’s amazing effect — reducing morbidity in the most impressive way,” she told Channel 12 news.
“What do we see now? We’re the first country where our elderly and immunocompromised were truly vaccinated [with the third shot] six months ago. We see that they don’t have neutralizing antibodies in the blood. We’re starting to see a little contagion among those in elderly care facilities,” Rahav added.
She acknowledged there is not yet comprehensive data on the fourth vaccine shot, but argued the chance that it is effective is far higher than the potential risk.
On Monday, national coronavirus czar Salman Zarka admitted 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.
Around two-thirds of Israel’s population of nearly 9.5 million have received at least one dose of the vaccine, and nearly 4.3 million Israelis have received three doses, according to the latest Health Ministry figures.