Pfizer-BioNTech vaccine greatly reduces symptomatic Covid-19 in the real world, say Israeli researchers

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The findings, while preliminary, suggest that the vaccine remains remarkably effective in a mass vaccination campaign – outside of the carefully controlled conditions of a clinical trial.

The Clalit Research Institute, part of a major Israeli health system, analyzed data from 1.2 million people, about half of whom had received the Pfizer-BioNTech vaccine. Researchers compared patients who had received the vaccine with similar individuals who had not.

The percentage of symptomatic Covid-19 – that is, people infected with the coronavirus and feeling sick – decreased by 94% in people who received two doses of the vaccine, according to a Clalit press release. The percentage of serious illnesses fell by 92%.

Full details of the study were not immediately available and the study has not yet been peer-reviewed. Still, the findings are consistent with data from Pfizer’s own vaccine study, which found the vaccine to provide 95% protection against symptomatic Covid-19.

In the Pfizer study, researchers randomly assigned patients to receive either the vaccine or a placebo. Then they looked at how many people got sick in each group and found that the vaccine greatly reduced the disease.

Pfizer’s study was a randomized controlled trial, the gold standard in clinical research. The Israeli study, on the other hand, was observational, meaning that researchers didn’t randomly choose who got the vaccine and who didn’t.

That can cause problems; For example, people who choose to get vaccinated are likely to take other measures to protect themselves.

However, researchers said they were trying to account for those kinds of effects. And observational studies are important because they can provide some insight into how well vaccines protect people under real-life conditions.

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