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. 2022 Jul 7;387(1):21-34.
doi: 10.1056/NEJMoa2203965. Epub 2022 Jun 15.

Effects of Previous Infection and Vaccination on Symptomatic Omicron Infections

Heba N Altarawneh  1 , Hiam Chemaitelly  1 , Houssein H Ayoub  1 , Patrick Tang  1 , Mohammad R Hasan  1 , Hadi M Yassine  1 , Hebah A Al-Khatib  1 , Maria K Smatti  1 , Peter Coyle  1 , Zaina Al-Kanaani  1 , Einas Al-Kuwari  1 , Andrew Jeremijenko  1 , Anvar H Kaleeckal  1 , Ali N Latif  1 , Riyazuddin M Shaik  1 , Hanan F Abdul-Rahim  1 , Gheyath K Nasrallah  1 , Mohamed G Al-Kuwari  1 , Adeel A Butt  1 , Hamad E Al-Romaihi  1 , Mohamed H Al-Thani  1 , Abdullatif Al-Khal  1 , Roberto Bertollini  1 , Laith J Abu-Raddad  1
Affiliations

Effects of Previous Infection and Vaccination on Symptomatic Omicron Infections

Heba N Altarawneh et al. N Engl J Med. .

Abstract

Background: The protection conferred by natural immunity, vaccination, and both against symptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection with the BA.1 or BA.2 sublineages of the omicron (B.1.1.529) variant is unclear.

Methods: We conducted a national, matched, test-negative, case-control study in Qatar from December 23, 2021, through February 21, 2022, to evaluate the effectiveness of vaccination with BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna), natural immunity due to previous infection with variants other than omicron, and hybrid immunity (previous infection and vaccination) against symptomatic omicron infection and against severe, critical, or fatal coronavirus disease 2019 (Covid-19).

Results: The effectiveness of previous infection alone against symptomatic BA.2 infection was 46.1% (95% confidence interval [CI], 39.5 to 51.9). The effectiveness of vaccination with two doses of BNT162b2 and no previous infection was negligible (-1.1%; 95% CI, -7.1 to 4.6), but nearly all persons had received their second dose more than 6 months earlier. The effectiveness of three doses of BNT162b2 and no previous infection was 52.2% (95% CI, 48.1 to 55.9). The effectiveness of previous infection and two doses of BNT162b2 was 55.1% (95% CI, 50.9 to 58.9), and the effectiveness of previous infection and three doses of BNT162b2 was 77.3% (95% CI, 72.4 to 81.4). Previous infection alone, BNT162b2 vaccination alone, and hybrid immunity all showed strong effectiveness (>70%) against severe, critical, or fatal Covid-19 due to BA.2 infection. Similar results were observed in analyses of effectiveness against BA.1 infection and of vaccination with mRNA-1273.

Conclusions: No discernable differences in protection against symptomatic BA.1 and BA.2 infection were seen with previous infection, vaccination, and hybrid immunity. Vaccination enhanced protection among persons who had had a previous infection. Hybrid immunity resulting from previous infection and recent booster vaccination conferred the strongest protection. (Funded by Weill Cornell Medicine-Qatar and others.).

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Figures

Figure 1
Figure 1. Effectiveness of Previous Infection, Vaccination with BNT162b2, and Hybrid Immunity against Symptomatic Omicron BA.1 and BA.2 Infection and against Severe, Critical, or Fatal Covid-19.
𝙸 bars indicate 95% confidence intervals. Covid-19 denotes coronavirus disease 2019.
Figure 2
Figure 2. Effectiveness of Previous Infection, Vaccination with BNT162b2 or mRNA-1273, and Hybrid Immunity against Any Symptomatic Omicron Infection and against Severe, Critical, or Fatal Covid-19.
𝙸 bars indicate 95% confidence intervals.
Figure 3
Figure 3. Effectiveness of Previous Infection, Vaccination, and Hybrid Immunity against Any Symptomatic Omicron Infection According to Time since Previous Infection or Vaccination.
𝙸 bars indicate 95% confidence intervals.
Figure 4
Figure 4. Effectiveness of Previous Infection, Vaccination with mRNA-1273, and Hybrid Immunity against Symptomatic Omicron BA.1 and BA.2 Infection and against Severe, Critical, or Fatal Covid-19.
𝙸 bars indicate 95% confidence intervals.
See this image and copyright information in PMC

References

    1. World Health Organization. Tracking SARS-CoV-2 variants. 2020. (https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/).
    1. Altarawneh HN, Chemaitelly H, Hasan MR, et al. Protection against the omicron variant from previous SARS-CoV-2 infection. N Engl J Med 2022;386:1288-1290. - PMC - PubMed
    1. Chemaitelly H, Ayoub HH, AlMukdad S, et al. Duration of mRNA vaccine protection against SARS-CoV-2 omicron BA.1 and BA.2 subvariants in Qatar. Nat Commun 2022;13:3082-3082. - PMC - PubMed
    1. Abu-Raddad LJ, Chemaitelly H, Ayoub HH, et al. Effect of mRNA vaccine boosters against SARS-CoV-2 omicron infection in Qatar. N Engl J Med 2022;386:1804-1816. - PMC - PubMed
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Supplementary concepts