Sunday 14 February 2021 8:30 pm

Pfizer vaccine cuts Covid-19 transmission risk four-fold, even before second dose: study

People vaccinated with the Pfizer vaccine are four times less likely to spread the Coronavirus, even before they have received their second jab, according to a new study.

Individuals who tested positive for Covid-19 and received at least their first vaccination had a much lower viral load than those who had not received any vaccine yet, researchers from Tel Aviv University and TIIT in Israel said yesterday.

The viral load was shown to be reduced fourfold on average for infections occurring 12 to 28 days after the first dose of the Pfizer-BioNTech vaccine, according to the study.

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It is reportedly the first study to draw conclusions on transmission risks by people confirmed to have been vaccinated.  

The study was based on positive post-vaccination samples, taken between 23 December 23 and 25 January. Patients who had a positive sample prior to vaccination were excluded.

‘Game changer’

Vaccine expert Cyrille Cohen, of Bar Ilan University, hailed the results of the TIIT study, reportedly calling them “a game changer.”

 “After all, transmissibility after the vaccine has been one of the most important questions we are asking ourselves,” Cohen said, who is a member of an Israeli Health Ministry advisory committee on coronavirus vaccines.

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“This shows that indeed, besides reducing symptoms and hopefully mortality, the vaccine may facilitate reaching some kind of herd immunity, allowing the partial protection of the weak or non-immunized.”

Real-world study

Israel’s rapid vaccination rollout has turned the country’s population into the largest real-world study of Pfizer’s Covid-19 vaccine. More than half of all Israelis, close to 4m people, have now received their first jab.

Among older people and those in vulnerable groups, those who were vaccinated first, infection rates have dropped dramatically.

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