More data from Israel's vaccination programme is suggesting the Pfizer jab prevents 94% of symptomatic infections.
This indicates the vaccine is performing just as well in a larger population as it did in the clinical trials.
It is proving highly effective at preventing illness and severe disease among all age groups, according to public health doctor Prof Hagai Levine.
"High vaccination coverage of the most susceptible groups" was key, he said.
Israel's largest health fund Clalit looked at positive tests in 600,000 vaccinated people and the same number of unvaccinated people, matched by age and health status.
It found 94% fewer infections among the vaccinated group.
This was based on test results in people's medical records, usually taken if they had symptoms or were a close contact of someone who had tested positive.
And the vaccine prevented almost all cases of serious illness.
This pattern was the same in all age groups - including the over-70s, who may have been under-represented in clinical trials.
The data has not yet been formally published.
But it "sends a message to other countries such as the UK" about the usefulness of the vaccine, said Prof Levine, and the need to get "very high" coverage of the groups most likely to become very ill from the virus.
He said he could not put a number on what proportion of the population would need to be immunised before restrictions could ease.
"We still don't know what the impact is on transmission," he said.
But we can say that, at least, "the vaccine is useful for personal protection", he added.
Prof Eran Segal, who is analysing data for the Israeli Ministry of Health, suggested Israel had to vaccinate 80% of its over-60s before learning of its effect on Covid-19 cases.
Israel is the first country in the world to see the impact of its vaccination programme, but it took significant population coverage and several weeks to reach this milestone.
Greater falls were seen in the over-60s who were vaccinated first and in cities that vaccinated their populations earlier - patterns not seen in earlier lockdowns. This provides strong evidence it was the vaccine, and not just the lockdown, driving down cases.
But Prof Segal warned falls had happened more slowly than expected, possibly because of the effect of the UK variant, which has become the dominant strain in Israel.
And he cautioned that, even with the "very rapid pace" of Israel's vaccination programme, there were still tens of thousands of people who were unprotected and could become severely ill if infected.
"We still have to exit our lockdown very cautiously," he said, or risk large numbers of people being hospitalised.
Israel has been experiencing a significant wave of infection and remains under strict measures - but with everyone over the age of 16 now entitled to get vaccine, the hope is at least the education system could be reopened too.
The country has also been met with criticism over questions about who should provide vaccines to the Palestinian territories.
Israel has only just also started to transfer some doses to Palestinians in the West Bank and Gaza, so that vaccinations can begin for front-line health workers.
Meanwhile it has given the full two doses to a quarter of its resident population.