Protection of hybrid immunity against SARS-CoV-2 reinfection and severe COVID-19 during periods of Omicron variant predominance in Mexico
Bibliographic record
Abstract
ABSTRACT BACKGROUND With widespread transmission of the Omicron SARS-CoV-2 variant, reinfections have become increasingly common. Here, we explored the role hybrid immunity, primary infection severity, and variant predominance on the risk of reinfection and severe COVID-19 during periods of Omicron predominance in Mexico. METHODS We analyzed reinfections in Mexico in individuals with ≥90 days from a previous primary infection using a national surveillance registry of SARS-CoV-2 cases from March 3 rd , 2020, until August 13 th , 2022. Immunity-generating events included primary infection, partial or full vaccination and vaccine boosting. Reinfections were matched by age and sex with controls with primary SARS-CoV-2 infection and negative RT-PCR or antigen test ≥90 days after infection to explore risk factors for reinfection and reinfection-associated severe COVID-19. We also explored the protective role of heterologous vs. homologous vaccine boosters against reinfection or severe COVID-19 in fully vaccinated individuals. RESULTS We detected 231,202 SARS-CoV-2 reinfections in Mexico, with most occurring in unvaccinated individuals (41.55%). Over 207,623 reinfections occurred during periods of Omicron (89.8%), BA.1 (36.74%) and BA.5 (33.67%) subvariant predominance and a case-fatality rate of 0.22%. Vaccination protected against reinfection, without significant influence of the order of immunity-generating events and provided >90% protection against severe reinfections. Heterologous booster schedules were associated with ∼11% and ∼54% lower risk for reinfection and reinfection-associated severe COVID-19 respectively, modified by time-elapsed since the last immunity-generating event. CONCLUSIONS SARS-CoV-2 reinfections have increased during periods of Omicron predominance. Hybrid immunity provides protection against reinfection and reinfection-associated severe COVID-19, with potential benefit from heterologous booster schemes. RESEARCH IN CONTEXT Evidence before this study We searched PubMed for the terms “SARS-CoV-2” AND “reinfection” AND “hybrid immunity” until November 20 th , 2022, and identified a few population studies previously conducted in Israel, Sweden, Qatar, United States and Canada which explored risk of reinfection and the protective role of hybrid immunity in individuals with one, two or three doses of COVID-19 vaccines, predominantly during periods of predominance of Omicron BA.1 and BA.2 subvariants. Notably, no studies were conducted in any Latin American country or reported on the benefit of heterologous booster schemes or the order of immunity-generating events. Added value of this study We report the results of nation-wide study in Mexico of over 230,000 SARS-CoV-2 reinfections, with ∼90% occurring during periods of Omicron predominance. We identified that vaccination provided additional benefit on reducing the risk of SARS-CoV-2 reinfection, with the highest benefit observed in individuals with complete vaccination and booster protocols prior to primary infection or with primary infection during periods of BA.1 and BA.2 subvariant predominance. Hybrid immunity also provides a substantial reduction in the risk of reinfection-associated severe COVID-19, with >90% reduction in risk compared to unvaccinated individuals with previous SARS-CoV-2 infection, regardless of the order of immunity-generating events. Finally, heterologous COVID-19 booster schedules were associated with ∼11% and ∼54% lower risk for reinfection and reinfection-associated severe COVID-19 respectively, modified by time-elapsed since the last immunity-generating event. Implications of all the available evidence Our results support that COVID-19 vaccination and boosters provide additional benefit to protect against SARS-CoV-2 reinfection and reinfection-associated severe COVID-19. The use of heterologous boosters appears to provide additional protection in previously infected individuals and such schemes may prove beneficial to increase vaccination coverage as newer, more transmissible variants emerge.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".