Natural immunity in Israel
Comparing SARS-CoV-2 natural immunity to vaccine-induced immunity: reinfections versus breakthrough infections
https://www.medrxiv.org/content/10.1101/2021.08.24.21262415v1
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
Qatar
https://www.nejm.org/doi/full/10.1056/NEJMc2200133
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
