Israeli study of 1.2m people confirms Pfizer vaccine is 94% effective

WASHINGTON • Pfizer's Covid-19 vaccine has been found to be 94 per cent effective in a study involving 1.2 million people in Israel, with the first major peer-reviewed real world research confirming the power of mass immunisation campaigns to bring the pandemic to a close.

The paper, which was published in the New England Journal of Medicine on Wednesday, also demonstrated there may be a strong protective benefit against infection, a crucial element in breaking onward transmission.

The experiment was carried out during a period when a variant first identified in Britain was rampant in Israel, making the vaccine's performance all the more impressive.

Between Dec 20 last year and Feb 1, each vaccinated participant was matched to an unvaccinated "control" person of similar age, sex, geographic, medical and other characteristics.

The researchers then recorded outcomes at days 14-20 after the first of the two doses and day seven or more after the second.

The efficacy against symptomatic infections was 57 per cent at 14-20 days after the first dose, but rose to 94 per cent seven days after the second dose - very close to the 95 per cent achieved during phase three clinical trials.

People who received second doses were also highly protected against hospitalisation and death, though the precise numbers are less significant and had a wider statistical range because of the relatively lower number of cases.

The study also found people who received their second dose had a 92 per cent lower chance of getting any form of infection at all compared with the unvaccinated.

While this finding was considered encouraging, the researchers and outside experts said there is a need for more evidence.

The authors attempted to correct for this with statistical methods but the result is still likely imperfect.

Biostatistician Natalie Dean from the University of Florida was certain there was a strong protective benefit, but added that "nailing down this number more precisely will require specialised study designs with frequent testing".

In England, people who have received two doses of the Pfizer vaccine are generating strong antibody responses as the shot is rolled out, researchers said yesterday, adding that confidence in vaccines was high.

The Imperial College London survey showed 87.9 per cent of people over the age of 80 tested positive for antibodies after two doses, rising to 95.5 per cent for those under the age of 60 and 100 per cent in those aged under 30.

Antibody levels are only one part of the immunity picture, with vaccines also shown to generate strong T-cell protection. T-cells are a type of white blood cell that helps the body fight infections.

Nearly 95 per cent of under-30s tested positive for antibodies 21 days after one dose. Antibody responses were generated in only 34.7 per cent of those 80 years or older, although Britain's Joint Committee on Vaccination and Immunisation has previously found high protection from the vaccine after one dose, even when antibody levels are lower.

Over 154,000 participants took part in Imperial's home surveillance study for Covid-19 antibodies between Jan 26 and Feb 8.

The survey also looked at confidence in vaccines, and showed it was high - with 92 per cent having accepted or planning to accept a vaccine offer. Confidence was lower among black people at 72.5 per cent.

AGENCE FRANCE-PRESSE, REUTERS