Immunity through Covid infection is much riskier than a vaccine

Spectator columnist Ross Clark, broadcaster Maajid Nawaz and the Times have all reported new Israeli research about Covid-19 immunity without an important piece of context. 

The research, which has not yet been peer-reviewed, does suggest that people who had been fully vaccinated against Covid with the Pfizer vaccine were about six times more likely to catch the virus than people who had caught it before, but not been vaccinated.

Vaccinated people were also about 13 times more likely to catch Covid, when compared with unvaccinated people who caught the disease more recently. Mr Clark, Mr Nawaz and the Times are right about this part of the research.

However, the group who seemed to have the highest level of protection were those who had been infected and received a single dose of the vaccine. The study found that people who were infected but not vaccinated were about twice as likely to test positive again, compared with this infected and vaccinated group.

In other words, even if the findings of this study are correct, people are still much more protected against Covid if they get vaccinated, whether they’ve caught it before or not.

“Natural immunity” is risky

Neither Mr Nawaz nor Mr Clark nor the Times report mention this latter finding. (Although the Bloomberg article cited by Mr Nawaz does.)

Mr Clark also says the research “suggests that we might be wasting our time trying to foist jabs on the young when they may have gained better, stronger immunity to Covid through natural infection”.

However, there are also the dangers of a Covid infection itself to consider. As the immunologist Dr Marion Pepper told the journal Science, the Israeli research does suggest that natural immunity may be more protective, but that “doesn’t take into account what this virus does to the body to get to that point”.

Full Fact asked Professor Charles Bangham, Chair in Immunology at Imperial College London, whether this study suggests that it might be better to allow young people to catch Covid rather than vaccinate them. He told us: “That is a complete non sequitur. Absolutely misconceived… You can’t argue that.

“The risks of infection are much greater than the risks of the vaccine. So it’s much safer, in almost all circumstances, to have the vaccine. There’s no question about that. ”

We still need to know more

As Mr Clark acknowledges, the Israeli research has not been peer-reviewed, so its conclusions are not yet a settled fact.

Dr Michael Head, senior research fellow in Global Health at the University of Southampton, told Full Fact via the Science Media Centre that there were “some limitations” to the study which, in his view, “somewhat negate the findings”.

“There is, for example, survivorship bias,” he said. “Those who died from COVID-19 cannot be included in this study, which will have a greater impact on the population within the ‘natural infection’ group than vaccinated populations...

“Population behaviours will also be important–will willingness to be tested differ between those previously infected and vaccinated? Will there also be differences in approaches to social distancing or wearing a mask? Any uncontrolled difference here may impact upon the take-up of testing and thus impact upon whether or not these are representative samples...”

However, Professor Bangham said: “I think [this study is] very likely to be correct. I'd see no reason to doubt it. More importantly, it's exactly what any immunologist would expect to be true.”

Professor Paul Hunter, Professor in Medicine at The Norwich School of Medicine at the University of East Anglia, agreed. He told Full Fact: “Yes, the balance of evidence does suggest that natural infection will provide a more durable immunity especially to severe disease.

“But of course the downside of that is that during your first natural infection if unvaccinated you are just as much at risk of severe disease and death depending on your age and other risk factors at any time during the pandemic.”