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Effectiveness of COVID-19 Vaccines in Older Adults in Colombia: First Report of the Esperanza Cohort. A Matched-Pair, National Study
18 Pages Posted: 16 Dec 2021
More...Abstract
Background: Although clinical trials showed that vaccines have a high efficacy and safety, differences in study designs and populations do not allow for comparison across products and age groups. The real-world effectiveness in population with the high risk of severe disease or death of a diversified portfolio of vaccines acquired by Colombia becomes important for assessing national vaccination plans and future decision-making.
Methods: We carried out a population-based matched-pair cohort study in 2828294 people 60 years and older. The exposed cohort consisted of older adults fully vaccinated with Ad26.COV2.S, BNT162b2, ChAdOx1 nCoV-19, or CoronaVac without history of Sars-CoV-2 infection. The follow-up was made between March 11 and October 26, 2021. To estimate effectiveness, we constructed cause-specific Cox survival models in presence of competitive risks (hospitalisation vs death due to COVID-19). Finally, we estimated the effectiveness of each vaccine adjusting by main potential confounders over each age group.
Findings: The overall effectiveness of vaccines to prevent hospitalisation without subsequent death was 61·6% (95% CI 58·0 - 65·0), to prevent death after hospitalisation for COVID-19, 79·8% (95% CI 78·5 - 81·1), and to prevent death without previous COVID-19 hospitalisation, 72·8% (95% CI 70·1 - 75·3). The effectiveness of vaccines to prevent death after hospitalisation for COVID-19 was 22·6 percentage points less in adults 80 and older compared with adults between 60 and 69 years old (68·4% vs 91·0%). We found statistically significant differences in effectiveness between vaccines in preventing hospitalisations and deaths.
Interpretation: The Ad26.COV2.S, BNT162b2, ChAdOx1 nCoV-19, and CoronaVac vaccines are effective in preventing hospitalisations and deaths caused by COVID-19 in fully vaccinated adults 60 years and older. BNT162b2 showed the highest effectiveness among this population. Effectiveness decreases with increasing age, regardless of the type of vaccine used in the primary scheme. An additional dose of the vaccine seems to be the best alternative for increase protection in older adults.
Funding Information: Colombian Ministry of Health and Social Protection.
Declaration of Interests: FRG, LAC and JFN are members of the Colombian COVID-19 vaccine advisory committee. All other authors declare no competing interests.
Ethics Approval Statement: 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.
Keywords: COVID-19, Vaccines, Survival Analysis, Pandemics, Cohort studies, Colombia
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