Large Israeli study: Natural immunity provides 13 times more protection against Delta than Pfizer's vaccine does

AP Photo/Jessica Hill

Big news from Maccabi Healthcare Services, which tracked many thousands of people for this (not yet peer-reviewed) study. If its findings are borne out, anyone who’s had COVID should be allowed to submit the results of a prior positive test in lieu of proof of vaccination wherever that’s required. After all, they’re much safer from the virus than the vaccinated are.

Israeli scientists compared three groups, those who’ve had both shots but never been infected, those who’ve been infected but haven’t had their shots, and those who’ve been infected and then had one shot. The third group was the most protected, but only slightly more than the natural immunity group was. That corresponds with other studies showing that infection plus vaccination equals the best possible immunity.

The surprise came when they compared the vaccinated group to the infected but unvaccinated group. Some scientists have speculated that vaccine immunity is actually superior to natural immunity in the belief that the shots produce a more diverse array of antibodies than infection does. That’s not what the Israelis found. Not only is natural immunity superior, it’s no contest. Especially in the age of Delta:

In model 1, we matched 16,215 persons in each group. Overall, demographic characteristics were similar between the groups, with some differences in their comorbidity profile (Table 1a).

During the follow-up period, 257 cases of SARS-CoV-2 infection were recorded, of which 238 occurred in the vaccinated group (breakthrough infections) and 19 in the previously infected group (reinfections). After adjusting for comorbidities, we found a statistically significant 13.06-fold (95% CI, 8.08 to 21.11) increased risk for breakthrough infection as opposed to reinfection (P<0.001). Apart from age ≥60 years, there was no statistical evidence that any of the assessed comorbidities significantly affected the risk of an infection during the follow-up period (Table 2a).

As for symptomatic SARS-COV-2 infections during the follow-up period, 199 cases were recorded, 191 of which were in the vaccinated group and 8 in the previously infected group. Symptoms for all analyses were recorded in the central database within 5 days of the positive RT-PCR test for 90% of the patients, and included chiefly fever, cough, breathing difficulties, diarrhea, loss of taste or smell, myalgia, weakness, headache and sore throat. After adjusting for comorbidities, we found a 27.02-fold risk (95% CI, 12.7 to 57.5) for symptomatic breakthrough infection as opposed to symptomatic reinfection (P<0.001) (Table 2b). None of the covariates were significant, except for age ≥60 years.

No contest. It’s above my pay grade to try to explain why the advantage is so stark but I assume it has to do with one’s immune system getting a better “look” at SARS-CoV-2 from infection than from vaccination. The vaccine instructs your body to produce the virus’s spike protein; that single component is what your immune system learns to recognize and attack. Someone who’s infected by the virus itself learns to recognize the whole organism, by contrast. If the spike protein on Delta looks sufficiently different from the spike protein on earlier variants, it stands to reason that a vaccinated person’s antibodies may have more difficulty responding to it. Whereas the antibodies in a person with natural immunity may recognize the virus itself and move rapidly to clear it even if the spike seems unfamiliar.

There’s a wrinkle to the Israeli findings. People who were infected with the virus and recovered more recently had a bigger advantage over the vaccinated than people who were infected last year did. The numbers above describe the comparative immunity of those who were either vaccinated or infected in January and February of this year. If you expand the group to include people who were infected between March and December 2020 as well, the relative advantage of natural immunity dipped to being six-fold better against infection and seven-fold better against symptomatic illness than the vaccines were. That’s still far superior, but it’s evidence that natural immunity wanes just like vaccine immunity does. Except more slowly, and from a way higher baseline.

Which means there’s good news and bad news. The good news is that if you insist on not getting vaccinated and end up being infected by Delta, you’ll have extremely strong immunity if you recover.

The bad news lies in the phrase “if you recover.” And even if you do, it may be a hard road. Another study from Israel found that, while it’s true that in rare cases vaccination can cause heart inflammation, COVID itself causes the same condition at a higher rate. In Israel, getting the jab led to an extra 2.7 cases of inflammation per 100,000 people versus 11 extra cases per 100,000 among COVID patients. There are also studies abroad floating around indicating that adults infected by Delta are more likely to have a severe illness than they were with previous variants, which may leave patients more susceptible to “long COVID.” In fact, despite more than half the population being vaccinated, the United States has more people in the hospital for COVID right now than it did a year ago at this time. And the great, great majority of them are unvaccinated.

Taking your chances with the virus is a high-stakes bet.

Anyway, Ross Clark writes today at the Spectator that these new findings may call for a rethink of national COVID strategies. Do they?

It suggests that the efficacy of the Pfizer vaccine — so impressive in trials — is not strong enough to bring about the kind of herd immunity we might have gained by letting the virus pass through the population. The same is probably true of other vaccines — as Kate wrote on Coffee House yesterday, recent studies have suggested that the efficacy of AstraZeneca declines over time, too, although not at quite the rate of the Pfizer one.

It also 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. But one of the most interesting issues is the new light it sheds on the debate over vaccinating children; perhaps it is better to simply allow them to be infected on the grounds they’re highly unlikely to come to serious harm but are more likely to gain lasting immunity from the disease that way.

“Letting the virus pass through the population” would come with a much higher body count than mass vaccination would. How many casualties does he have in mind?

The point about children is interesting but I don’t see why he’s treating vaccine immunity and natural immunity as an either/or. After all, there’s a missing fourth group from the Israeli study that scientists didn’t examine, people who got both shots and then got infected. What sort of immunity do they have relative to everyone else? The same as those with natural immunity or the same as the infection + one dose group? Or better than that? There are plenty of young-ish unvaccinated Americans landing in ERs due to Delta; vaccination would have almost certainly averted that outcome for them. If Delta is so hyper-contagious that we’re all destined to get it eventually, it seems to me the strategy should be to build a baseline of immunity via vaccination to prevent the infection from becoming severe and then count on natural immunity post-infection to create durable protection against getting the virus again. It’s not either/or.

I’ll leave you with this clip of nurses in Mississippi quitting because they can’t cope with the patient load from unvaccinated patients. Something else to consider before we switch to the ol’ herd immunity herp derp strategy.

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