Natural immunity in Israel

Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections

https://www.medrxiv.org/content/10.11...

Early vaccinees were demonstrated to be significantly more at risk than late vaccinees

Maccabi Healthcare Services

N = 2.5 million

26% of the population

Provides a representative sample of the Israeli population

Study comparing three groups

SARS-CoV-2-naïve individuals with 2 doses of Pfizer (n = 673,676)

Previously infected, not been vaccinated (n = 62,883)

Previously infected with one dose of Pfizer (n = 42,099)

We evaluated four outcomes

June 1st to August 14th 2021 (Delta times)

SARS-CoV-2 infection

Symptomatic disease

COVID-19-related hospitalization

Deaths

Results

SARS-CoV-2-naïve individuals with 2 doses of Pfizer (no infection, doubly vaccinated)

(Only with vaccine protection)

If first exposure every (infection or vaccination) was in Jan or Feb 2021

13.06-fold increased risk for breakthrough infection compared to those previously infected

Comparing infections in vacationed with previously infected

238 infections in the vaccinated group

19 infections in the previously infected (not vaccinated) group

Increased risk of symptomatic disease

fever, cough, breathing difficulties, diarrhea, loss of taste or smell, myalgia, weakness, headache and sore throat

191 cases in the vaccinated group

8 in the previously infected group

Significant (P less than 0.001)

Increased risk of hospital admission

8 admissions in the vaccinated group
1 in the previously infected group
Deaths

No deaths in either group

March 2020 to February 2021

Evidence of waning natural immunity was demonstrated

But

SARS-CoV-2 naïve vaccinees (i.e. vaccinated but no natural infection)

5.96-fold increased risk for breakthrough infection

7.13-fold increased risk for symptomatic disease

Previously infected vs. vaccinated and previously infected individuals

Previously infected individuals to those who were both previously infected and received a single dose of the vaccine

20 infections in the infected plus one vaccine dose

37 infections in the infected but no vaccine group

No deaths in either group

Conclusions

This study demonstrated that natural immunity confers longer lasting and stronger protection,

against infection, symptomatic disease and hospitalization caused by the Delta,

compared to the BNT162b2 two-dose vaccine-induced immunity

Individuals who were both previously infected with SARS-CoV-2 and given a single dose of the vaccine gained additional protection against the Delta variant

Question 2: Are the data on natural immunity also valid for the Omicron variant?

Answer: Yes, (Letter to NEJM)
Protection against the Omicron Variant from Previous SARS-CoV-2 Infection

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https://www.nejm.org/doi/full/10.1056...

In addition, we performed
sensitivity analyses that included adjustment for vaccination status and that excluded vaccinated persons from the analysis.

Protection against reinfections is moderately lower for the Omicron variant

The effectiveness of previous infection in preventing reinfection was estimated to be

90.2% against the alpha variant

85.7% against the beta variant,

92.0% against the delta variant, and

56.0%magainst the omicron variant

Protection against severe, critical or fatal COVID-19 is similar as for other variants

The effectiveness with respect to
severe, critical, or fatal Covid-19

69.4% against the alpha variant,

88.0% against the beta variant

95% to 100% against the delta variant

87.8% against the omicron variant

The median interval between previous infection and PCR testing

254 days to 376 days