Decrease in COVID-19 adverse outcomes in adults during the Delta and Omicron SARS-CoV-2 waves, after vaccination in...

Area of Science:

• Epidemiology
• Public Health
• Vaccinology

Background:

• Mexico experienced high COVID-19 mortality, with over 5.1 excess deaths per 1,000 inhabitants.
• The national vaccination strategy prioritized the elderly population against SARS-CoV-2.
• Seven diverse vaccines were utilized amid high virus circulation.

Purpose of the Study:

• To evaluate the effectiveness of Mexico's COVID-19 vaccination strategy.
• To assess the impact of vaccination on severe COVID-19 outcomes during Delta and Omicron waves.
• To analyze vaccine impact on pregnant individuals and pediatric populations.

Main Methods:

• Retrospective cohort study using national health authority data.
• Analysis of COVID-19 cases, hospitalizations, deaths, and excess deaths.
• Stratification by age group and pandemic wave (Delta and Omicron variants).

Main Results:

• Vaccinating the eldest third reduced hospitalizations and deaths by 46-55% (Delta wave).
• Outcomes decreased by 74-85% (Omicron wave) after broader adult vaccination.
• Vaccinating pregnant individuals significantly reduced fatalities in mothers and infants.
• Unvaccinated children experienced over 40% increase in hospitalizations during Delta and Omicron waves.

Conclusions:

• Mexico's vaccination strategy successfully reduced population mortality and severe COVID-19.
• Continued vaccination efforts are crucial, especially for children, to mitigate severe COVID-19.
• Extending SARS-CoV-2 vaccine access to children, particularly those aged 1-4, is recommended.