Dataset Information

Effects of Previous Infection and Vaccination on Symptomatic Omicron Infections.

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.).

SUBMITTER: Altarawneh HN

PROVIDER: S-EPMC9258753 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundLittle is known about protection against SARS-CoV-2 infection following previous infection with specific individual SARS-CoV-2 variants, COVID-19 vaccination, and a combination of previous infection and vaccination (hybrid immunity) in adolescents. We aimed to estimate protection against symptomatic PCR-confirmed infection with the delta (B.1.617.2) and omicron (B.1.1.529) variants in adolescents with previous infection, mRNA vaccination, and hybrid immunity.MethodsWe conducted an observational, test-negative, case-control study using national SARS-CoV-2 testing and COVID-19 mRNA vaccination data in England. Symptomatic adolescents aged 12-17 years who were unvaccinated or had received primary BNT162b2 immunisation at symptom onset and had a community SARS-CoV-2 PCR test were included. Vaccination and previous SARS-CoV-2 infection status in adolescents with PCR-confirmed COVID-19 (cases) were compared with vaccination and previous infection status in adolescents who had a negative SARS-CoV-2 PCR test (controls). Vaccination data were collected from the National Immunisation Management System, and were linked to PCR testing data. The primary outcome was protection against SARS-CoV-2 delta and omicron infection (defined as 1 - odds of vaccination or previous infection in cases divided by odds of vaccination or previous infection in controls).FindingsBetween Aug 9, 2021, and March 31, 2022, 1 161 704 SARS-CoV-2 PCR tests were linked to COVID-19 vaccination status, including 390 467 positive tests with the delta variant and 212 433 positive tests with the omicron variants BA.1 and BA.2. In unvaccinated adolescents, previous SARS-CoV-2 infection with wildtype, alpha (B.1.1.7), or delta strains provided greater protection against subsequent delta infection (>86·1%) than against subsequent omicron infection (<52·4%); previous delta or omicron infection provided similar protection against omicron reinfection (52·4% [95% CI 50·9-53·8] vs 59·3% [46·7-69·0]). In adolescents with no previous infection, vaccination provided lower protection against omicron infection than against delta infection, with omicron protection peaking at 64·5% (95% CI 63·6-65·4) at 2-14 weeks after dose two and 62·9% (60·5-65·1) at 2-14 weeks after dose three, with waning protection after each dose. Adolescents with hybrid immunity from previous infection and vaccination had the highest protection, irrespective of the SARS-CoV-2 strain in the primary infection. The highest protection against omicron infection was observed in adolescents with vaccination and previous omicron infection, reaching 96·4% (95% CI 84·4-99·1) at 15-24 weeks after vaccine dose two.InterpretationPrevious infection with any SARS-CoV-2 variant provided some protection against symptomatic reinfection, and vaccination added to this protection. Vaccination provides low-to-moderate protection against symptomatic omicron infection, with waning protection after each dose, while hybrid immunity provided the most robust protection. Although more data are needed to investigate longer-term protection and protection against infection with new variants, these data question the need for additional booster vaccine doses for adolescents in populations with already high protection against SARS-CoV-2 infection.FundingNone.

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