Bloomberg reports that early data from Israel shows that people who recovered from Covid may face a significantly lower risk from the Delta Covid variant than those fully vaccinated with the Pfizer-BioNTech jab.
The groundbreaking findings – which could influence public health policies around the globe – from the largest real-world study comparing natural immunity gained from earlier infection with the protection provided by one of the most effective jabs showed that reinfections were much less common among those who had caught Covid.
The data, posted as a preprint article on medRxiv, has not yet been reviewed by other researchers, and therefore should be treated with some caution. The results contrast with earlier studies suggesting immunisation offered better protection than prior infection, though those studies did not assess the Delta variant, Bloomberg reported.
However, the results were stark. People given both doses of Pfizer-BioNTech were almost six times more likely to contract Delta and seven-fold more likely to have symptomatic disease than those who had previously recovered.
“This analysis demonstrated that natural immunity affords longer lasting and stronger protection against infection, symptomatic disease and hospitalisation due to the delta variant,” the researchers said.
Protection from an earlier infection also wanes significantly with time, the analysis suggested.
The study will raise serious questions over the decision of the US Food and Drug Administration to award the Pfizer jab full approval this week.
It comes after a Science Magazine report last week suggested breakthrough infections were far more common than the term suggests, with 60% of hospitalised patients with Covid in Israel fully vaccinated despite 78% of those 12 and older in the country being fully vaccinated.
The sheer number of vaccinated Israelis means some breakthrough infections were inevitable, and the unvaccinated are still far more likely to end up in the hospital or die. But Israel’s experience is forcing the booster issue on to the radar for other nations, suggesting as it does that even the best vaccinated countries will face a Delta surge.
Now, the effects of waning immunity may be beginning to show in Israelis vaccinated in early winter; a preprint published last month by physician Tal Patalon and colleagues at KSM, the research arm of MHS, found that protection from Covid-19 infection during June and July dropped in proportion to the length of time since an individual was vaccinated. People vaccinated in January had a 2.26 times greater risk for a breakthrough infection than those vaccinated in April. (Potential confounders include the fact that the very oldest Israelis, with the weakest immune systems, were vaccinated first.