Anyone worried that Covid-19 vaccine efficacy might not hold up outside the rigorous clinical trial setting should be reassured today. Data from Israel’s vaccination programme have found levels of protection against Covid-19 with Pfizer/Biontech’s Comirnaty that are almost equal to those seen in the groups’ pivotal trial.
The results, published today in the NEJM, again highlight the impressive efficacy of the mRNA vaccine as the world eagerly awaits more late-stage Covid-19 vaccine data, notably those from the US pivotal study of Astrazeneca’s AZD1222.
The latest data with Comirnaty, also known as BNT162b2, come from over a million people in Israel, comprising just under 597,000 who received the vaccine and the same number of matched unvaccinated control subjects.
Two doses of the vaccine were 94% effective in preventing symptomatic Covid-19. This was the primary endpoint of Comirnaty’s pivotal trial, which found 95% efficacy.
In the Israeli experience Comirnaty also did well in preventing severe disease, hospitalisations and deaths. Efficacy was similar across different age groups.
|Comirnaty's real-world performance in Israel|
|Estimated vaccine effectiveness|
|14-20 days after 1st dose||21-27 days after 1st dose||
≥7 days after 2nd dose
|Source: NEJM article.|
The Israeli results come just days after the publication of two Lancet preprints detailing promising real-world results in the UK. On Friday, data from the EAVE II project showed that, in Scotland, one dose of Comirnaty or AZD1222 reduced Covid-19-related hospitalisations by 85% and 94% respectively.
And on Monday the Siren study in healthcare workers found that even one dose of Comirnaty was 72% effective in preventing symptomatic and asymptomatic Covid-19 alike. With two doses, efficacy rose to 86%.
Data with AZD1222 were not given, but Public Health England said it was monitoring the real-world impact of the Astra vaccine, and early signs showed "good levels of protection from the first dose".
Still, there are lingering questions about AZD1222’s true efficacy after the confusing analysis of Astra’s pivotal UK and Brazil trials, on which its UK and European authorisations were based.
Astra claimed an efficacy rate of 70%, pooled across both trials, but this result was flattered by better results in people who received a half dose followed by a full dose; the efficacy figure for the standard-dose regimen was 62%.
To complicate things further, another analysis has found 82% efficacy with AZD1222 when the first and second doses were given 12 weeks apart, versus just 55% when the dosing interval was less than six weeks.
This might not bode well for the upcoming US pivotal trial readout, expected this quarter; in that study the first and second doses of AZD1222 are given four weeks apart.