Is Israel or the UK right about the effectiveness of the COVID-19 vaccine?

Two separate studies, one published by Israel’s Ministry of Health and the other published in the New England Journal of Medicine late Thursday, showed striking differences.

“This discrepancy is a bit disturbing and needs to be investigated further,” said Professor Cyrille Cohen, member of the SARS-COV2 Vaccine Clinical Trials Advisory Committee at the Ministry of Health.

Specifically, the ministry study found that Pfizer’s coronavirus vaccine was only 40% effective against symptomatic cases of COVID-19 and 39% effective in stopping infection against the Delta variant.

However, he showed that the vaccine remains 91% effective against the development of severe cases of the disease and 88% against hospitalization.

The British study, in contrast, found that two doses of the Pfizer vaccine were 88% effective in stopping symptomatic Delta variant infection.

According to Cohen, there are several possible answers to the lack of data.

FIRST and critical is the time difference between exposure to the Delta variant and vaccination.

England vaccinated at a much slower rate than Israel, meaning that the majority of its population was not fully vaccinated until mid-April 2021. This contrasts with Israel, where around 90% of the the country’s most vulnerable population was vaccinated at the end of January.

It is starting to become clear that immunity to the vaccine begins to wane after about six months. The Israeli study showed that for people vaccinated more than six months ago, the vaccine’s effectiveness in stopping the coronavirus fell to 16%.

Of the more than 1.8 million people who received two injections as of January 31, some 5,770 have contracted the virus – and 1,181 of them, or 20% of all new infections, were contracted during the week of July 11-17, the health ministry reported.

“If you take into account that they [the UK population] vaccinated later and were exposed to the Delta variant a month before us, “Cohen said,” it might make sense that by the time they checked they were around 80% effective. The question is, what will happen in three months? Will they see the same efficiency that we are seeing? “

THE NEXT problem is age.

Israel and the UK have been careful to vaccinate healthcare workers and the elderly first. In England, however, the older population largely received the AstraZeneca vaccine, while people under 40 were offered Pfizer or Moderna as an alternative due to evidence linking AstraZeneca to rare blood clots. The same study showed that the AstraZeneca vaccine was only 67% effective against symptomatic disease after two doses.

In Israel, everyone received Pfizer. Breakthrough infections were most prominent among people 60 and older, a cohort that already has a greater tendency to be immunocompromised and prone to developing symptomatic if not severe cases of COVID-19.

A third explanation concerns the level of PCR tests carried out in the two countries. Israel uses a more sensitive or stricter PCR testing regime than the UK.

The genetic material of the virus is amplified in cycles by PCR tests. The more cycles there are, the more likely the lab is to detect the virus. Israel uses 37 cycles of amplification, which means you are positive for the coronavirus even though the testing process took up to 37 cycles to detect the virus.

“If the PCR tests are less sensitive, England may miss some cases – or Israel may catch more – and that could play a role in the numbers,” Cohen said.

FINALLY, a separate study released over the weekend by the UK Department of Health and Welfare found that an eight-week gap between the first and second dose of Pfizer vaccine is an “sweet spot” when it s ‘acts to generate neutralizing antibodies. .

When England launched its vaccination campaign, it did not have enough doses to vaccinate the population according to Pfizer’s recommended regimen of two doses three weeks apart. As such, he split the doses between four and 12 weeks to allow more people to receive at least one jab.

Specifically, the new research showed that the levels of neutralizing antibodies, the level of those antibodies responsible for the defense of cells against pathogens, were higher after the extended dosing interval (six to 14 weeks) compared to on the conventional diet for three to four weeks.

In contrast, the T cell response was of a slightly lower amplitude after the longer dosing interval. T cells provide longer-term immunity and scientists believe they may provide some immunity to COVID-19, even when antibodies become less effective in fighting the disease.

“The question is: would you wait eight weeks in the event of a pandemic? Cohen asked, noting that separate studies have shown that one dose of Pfizer vaccine is only about 30% effective against the Delta variant, which would leave the population vulnerable for two months. “This is a difficult question.”

Cohen’s solution is to provide the most vulnerable people with a third injection, which new research is starting to show does a good job of boosting antibody levels.

“We are still learning the best way to vaccinate people with these vaccines,” he said. “But we are still in the middle of the pandemic. “