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UPDATE 1-Israeli studies find Pfizer COVID-19 vaccine reduces transmission

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Maayan Lubell
·4 min read
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(releads, adds separate Israeli study finds vaccine reducestransmission, comments from scientists)

By Maayan Lubell

JERUSALEM, Feb 19 (Reuters) - Pfizer's COVID-19 vaccinegreatly reduces virus transmission, two Israeli studies havefound, shedding light on one of the biggest questions of theglobal effort to quash the pandemic.

Data analysis in a study by the Israeli Health Ministry andPfizer Inc found the Pfizer vaccine developed withGermany's BioNTech reduces infection, including inasymptomatic cases, by 89.4% and in syptomatic cases by 93.7%.

Findings of the pre-published study, not yet peer-reviewed,but based on a national database that is one of the world's mostadvanced, were first reported by the Israeli news site Ynet lateon Thursday and were obtained by Reuters on Friday.

Pfizer declined to comment and the Israeli Health Ministrydid not respond to a request for comment.

A separate study by Israel's Sheba Medical Center publishedon Friday in The Lancet medical journal found that among 7,214hospital staff who received their first dose in January, therewas an 85% reduction in symptomatic COVID-19 within 15 to 28days with an overall reduction of infections, includingasymptomatic cases detected by testing, of 75%.

More research is needed to draw a definitive conclusion, butthe studies are among the first to suggest a vaccine may stopthe spread of the novel coronavirus and not just prevent peoplegetting ill.

Michal Linial, a professor of molecular biology andbioinformatics at Jerusalem's Hebrew University, said thefindings were a big step towards answering one of the mostimportant questions in combating the pandemic.

"Whether it is 75 or 90 percent reduction doesn't matter -it is a big drop in transmission," Linial said. "It means thatnot only is the individual vaccinated protected, the inoculationalso provides protection to his or her surroundings."

The researchers said further study was needed onasymptomatic transmission among people fully vaccinated becausethey are less likely to be tested for COVID-19.

Vaccine developers have also said more research was neededon transmissibility. In December, Germany's BioNTech said itwould take three to six months more study.


Leading the world in its vaccination roll out, Israel'suniversal healthcare and advanced data capabilities haveprovided a nationwide database that can offer insights into howeffective the vaccines are outside controlled clinical trials.

The Health Ministry/Pfizer study analysed data collectedbetween Jan. 17 and Feb. 6, looking at individuals who had beenfully vaccinated, after receiving their second Pfizer shot.

To date more than 30%, or 2.8 million of Israel's ninemillion population have received both doses.

Sheba's study found that just the first dose of Pfizer'svaccine was 85% effective, potentially fuelling a debate overthe recommended two-dose schedule.

Canadian researchers in a letter published this weeksuggested that the second Pfizer dose be delayed given the highlevel of protection from the first shot to increase the numberof people getting vaccinated.

The U.S. Food and Drug Administration said in December datafrom those trials showed the vaccine began conferring someprotection to recipients before they received the second shot,but more data would be needed to assess the potential of asingle-dose shot.

Pfizer has said alternative dosing regimens of the vaccinehave yet to be evaluated and that the decision resided with thehealth authorities.

Another caveat is that the cohort studied at the hospitalwere "mostly young and healthy," Sheba epidemiologist GiliRegev-Yochay said.

Unlike with Pfizer's clinical trial, "we don't have many(staff) here aged over 65," she told reporters. But she alsosaid the Sheba study took place during a surge in coronavirusinfections in Israel, which flooded hospitals with new cases.

Pfizer declined to comment on the data, saying in astatement it was doing its own analysis of "the vaccine’sreal-world effectiveness in several locations worldwide,including Israel".

Both studies' findings compared with overall efficacy ofaround 95% in a two-dose regimen 21 days apart. The HealthMinistry/Pfizer researchers found the vaccine to be effectiveagainst the British coronavirus variant that makes up about 80%of Israel's confirmed cases.

Eran Kopel, an epidemiologist at Tel Aviv University saidthe Sheba study was important, but it focused on one hospitaland a relatively small group of people, so "one could not drawclear-cut epidemiological conclusions from it".

The Health Ministry's data was encouraging, he said, butfurther research and regular surveys were needed.

"The vaccinations are a very good tool but this is hardlythe end. This is a dynamic virus that has surprised thescientific world with its fast pace of change and variety," hesaid.(Additional reporting by Dan Williams in Jerusalem; Editing byJane Merriman and Barbara Lewis)