Effectiveness of COVID-19 Vaccines in Preventing Hospitalizations and Deaths in Colombia: A Pair-Matched, National-Wide Cohort Study in Older Adults
13 Pages Posted: 19 Oct 2021
Date Written: October 16, 2021
Background: Currently, Colombia is carrying out the National Vaccination Plan against COVID-19. Clinical trials of vaccines used in the country have a high efficacy and safety, but information on effectiveness is needed. We assessed the real-world effectiveness of the highly diversified portfolio of vaccines acquired by Colombia in fully vaccinated individuals 60 years and above.
Methods: We carried out a population-based cohort study in 3,346,826 people 60 years and older, matched 1:1 by sex, age, health system affiliation regime, presence of comorbidities, and municipality of residence. The exposed cohort consisted of older adults fully vaccinated with Ad26.COV2.S (Janssen), BNT162b2 (Pfizer), ChAdOx1 nCoV-19 (Oxford/AstraZeneca), or CoronaVac (Sinovac) without history of Sars-CoV-2 infection. The follow-up was made between March 11th and August 11th, 2021. To estimate effectiveness, we constructed cause-specific Cox survival models in presence of competitive risks (hospitalization vs death due to COVID-19), adjusted for main potential confounders.
Findings: The overall effectiveness of vaccines to prevent hospitalization was 69·9% (95% CI 65·5% - 73·7%), to prevent post-hospitalization death, 79·4% (95% CI 77·2 % - 81·4%) and to prevent death without hospitalization, 74·5% (95% CI 71·1% - 77·5%). The effectiveness of vaccines to prevent death after hospitalisation for Covid-19 was 27·7 percentage points less in adults 80 and older compared with adults between 60 and 69 years old (69·0% vs. 96·7%). Effectiveness of vaccines decreased with increasing age. We did not find a statistically significant difference in effectiveness between vaccines used in preventing hospitalisation or death.
Interpretation: The Ad26.COV2.S, BNT162b2, ChAdOx1 nCoV-19, and CoronaVac vaccines are effective in preventing hospitalization and death caused by COVID-19 in adults 60 years and older fully vaccinated. Effectiveness decreases with increasing age, regardless of the type of vaccine used in the primary scheme. An additional dose seems the best alternative for increase protection in population 70 and above.
Note: Ethics: This investigation complies with the scientific, technical, and administrative regulation for human health research in Colombia, which classifies this study as research without risk since it only used secondary data sources of anonymised information. Due to its characteristics, this study does not require the review or approval of a research ethics committee.
Funding: This study was carried out by Ministry of Health and Social Protection of Colombia workers from the Directorate of Medicines and Health Technologies and Directorate of Epidemiology. Funding from the Ministry was given indirectly through the wages and payments to some of the project participants.
Declaration of interests: FRG, LAC and JFN are members of the Colombian Covid-19 vaccine advisory committee. All other authors declare no competing interests. Other authors declare no competing interests.
Keywords: COVID-19; Vaccine effectivenes; Survival Analysis; Pandemics; Cohort studies; Colombia
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