Abstract
BACKGROUND: A SARS-CoV-2 (COVID-19) vaccination campaign was launched in Argentina in January 2021. The vaccines then available were administered to the population in several different schemes. This observational study presents a quantification of the impact of the different schemes on the probability of death for confirmed COVID-19 cases in Argentina's Buenos Aires Province. The results provide a local measure of the schemes' effectiveness that heretofore has been lacking. METHODS: The study's main source of information is the Integrated Health Information System database, which contains 1,538,113 records of confirmed SARS-CoV-2 (COVID-19) cases reported in 2021 in the Province. To assess the real-world effectiveness of the vaccination campaign, two categorical variables representing vaccination status were defined. Probability of death was formulated as a generalized linear model with a logistic link and includes variables for geography, a socio-economic level index, symptom onset, sex, and vaccination status. The effectiveness level was derived from the death probability estimates. FINDINGS: The study's findings indicated that the most effective vaccine was rAd26-rAd5 (Sputnik), with ChAdOx1-S (AZ/Covishield) and BBIBP-CorV (Sinopharm) following in efficacy, for both single and multiple doses. The effectiveness of a single dose was consistently below 50%, while it ranged from 50% to 90% for two or more doses. Notably, the analysis of variables such as the municipality of residence of the infected persons and the season of symptom onset yielded particularly intriguing insights. The socioeconomic level of a municipality emerged as a moderately strong predictor of the probability of death, which was marginally higher in municipalities with lower-income populations. Additionally, the data revealed an increased probability of death during the winter season. INTERPRETATION: The vaccination campaigns carried out in Buenos Aires Province in 2021 significantly contributed to reducing the number of deaths due to SARS-CoV-2 (COVID-19) among its population. However, the extent of this impact varied considerably depending on individual characteristics such as age, health status, and vaccination schedule adherence.