Effect of vaccination on household transmission Province of Santa Fe, Argentina, 2021

Abstract

INTRODUCTION: In 2019, a new coronavirus emerged causing a global pandemic. During 2020, vaccines with acceptable safety and efficacy were developed to reduce complications and deaths. The present work set out to investigate the relationship between vaccination and contagion between partners. METHODS: Data from the Federal Register of Nominalized Vaccination and confirmed cases in the province of Santa Fe registered in the Argentine Integrated Health Information System from January 1 to June 30, 2021 in people aged 18 to 65 years were analyzed. 5,291 pairs of an index case and a secondary case were constituted, whose addresses coincided and whose dates of onset of symptoms were in a range of 2 to 14 days. Pairs were selected in which one person was vaccinated and the other was not, with a total of 494 pairs. RESULTS: The average age of the index cases was 40.8 years and that of the secondary cases was 40.5 years. There were 234 vaccinated people among the index cases and 386 among the secondary ones. Of the 494 pairs with one vaccinated and one unvaccinated person, the index case was the vaccinated person in 179 pairs, and in 315, the index was the unvaccinated person. DISCUSSION: The analysis suggests that, in home infections, where vaccinated and unvaccinated people are involved, it is more common for the unvaccinated person to be the index case. This points to the importance of vaccinating the partners of people with risk factors.