Does natural immunity against SARS-CoV-2 infection protect better against the Delta variant than vaccination?

A new Israeli study suggests that immunity gained after recovering from a previous COVID-19 infection is more protective against the new Delta variant than vaccine-induced immunity. It was estimated that natural immunity was approximately 13 times stronger than having two doses of the Pfizer-BioNTech vaccine.

Researchers write:

This study showed that natural immunity confers more lasting and stronger protection against infection, symptomatic disease, and hospitalization caused by the Delta variant of SARS-CoV-2, compared with vaccine-induced immunity. dose BNT162b2 “.

However, vaccines may add an additional boost to protection in people who recovered from COVID-19. The results showed that a single dose of vaccine with natural immunity provided greater protection against reinfection than people with natural immunity.

The study “Comparing the natural immunity of SARS-CoV-2 with vaccine-induced immunity: reinfections against advanced infections” is published in medRxiv* prepress server.

How they did it

The research team compared the rate of SARS-CoV-2 infection, disease severity, hospitalization, and death in people over 16 who had natural or vaccine-induced immunity.

There were three groups in the study: 673,676 individuals who were fully vaccinated with the Pfizer-BioNTech vaccine and without prior exposure to SARS-CoV-2; 62,883 unvaccinated individuals who recovered from COVID-19; and 42,099 individuals with a previous SARS-CoV-2 infection who had received a single dose of vaccine.

The research team followed up with study participants from June 1 to August 14, 2021. The follow-up period occurred when the Delta variant was common in Israel.

Israel had one of the fastest vaccine launches in the world. Currently, more than 13 million doses have been administered in the country. As a result, the findings constitute the largest real-world observational study comparing natural immunity with the vaccine.

Increased advanced infections and hospitalizations in vaccinated individuals

People vaccinated without prior SARS-CoV-2 exposure had a 13.06-fold higher risk of becoming infected with the Delta variant. In addition, there was a 27-fold high risk of symptomatic COVID-19 infection.

Although the results could suggest a decrease in natural immunity against the Delta variant, vaccinated people still have a 5.96 times higher risk of advanced infection and a 7.13 times higher risk of suffering from symptomatic diseases compared with those previously infected, ”the researchers explained.

In addition, vaccinated individuals showed a higher risk of requiring hospitalization for an advanced infection than unvaccinated individuals with natural immunity.

People with a single dose of vaccine and who had previously recovered from the infection appeared to have more protection against Delta than unvaccinated people with natural immunity.

No COVID-19-related deaths were observed in all three groups.

Further research is needed on the long-term protection of natural immunity. However, researchers theorize that natural immunity could provide a greater immune response to SARS-CoV-2 proteins than the immune activation of anti-ear proteins offered by the Pfizer-BioNTech vaccine.

Study the limitations and points to consider

The study may have underestimated the number of asymptomatic infections because it collected its data from PCR tests. People with asymptomatic infections are less likely to get tested for SARS-CoV-2, suggesting that the results apply primarily to symptomatic infections.

The findings also focused on patients who received the Pfizer-BioNTech vaccine in early 2021. Other Israeli research has recently suggested that vaccine-induced antibody levels decrease after several months, but booster shots may improve the immune response. The comparison of natural immunity with vaccine-induced immunity with booster traits is unknown.

In addition, the results of the study do not translate into non-mRNA-based vaccines, such as AstraZeneca-Oxford and Johnson & Johnson vaccines.

The study focused primarily on the Delta variant, which has spread to many countries, including Israel. Because Delta was more common during the study, the results cannot assess how natural immunity protects against other variants of SARS-CoV-2.

Finally, the researchers acknowledge that different health behaviors, such as adherence to social distancing and wearing masks, could not be controlled in the study and may have affected the risk of becoming infected.

* Important news

medRxiv publishes preliminary scientific reports that are not reviewed by experts and therefore should not be considered conclusive, guide clinical practice / health-related behavior, or treated as established information.