Loss of control of the pandemic during vaccination in Uruguay

Abstract

In countries where lockdown was not strictly enforced during vaccination and the vaccination rate was near 1% of the population per day, a loss of control or a multiplying effect in virus spread was observed when the vaccination program was implemented. Particularly, in Uruguay between March and June 2021, there was a clear link between the vaccination rate and the number of positive cases of SARS-CoV-2 observed each day. The peaks in the vaccination rate by day were followed by peaks in positive cases with an 8-day lag. Typically, 10% to 20% non-detected positive cases are considered superspreaders due to their high viral load despite experiencing mild or no symptoms. These superspreaders or undetected positive cases were responsible for 80% of the virus's spread. The data we got access to allow us to define a cohort study for whole individuals being vaccinated during 5 consecutive days during March 2021 when vaccination starts. In this cohort there was a 75% reduction in tested positive cases in vaccinated individuals compared to what was expected. We have some extra data that suggest these number were maintained during the 4 months with high vaccination rate. We propose that this reduction is due to individuals they thought they were experiencing side effects from the vaccine and were not tested, but in fact they had COVID. These non-tested positives individuals, representing nearly 5% of positive cases per day, may have unknowingly become superspreaders, increasing the odds ratio to be infected during vaccination by 1.20x to 1.4x compared to a non-vaccination situation with same control measures applied. Previously, Uruguay had been considered one of the first countries in the world in pandemic management for a year without vaccination, with a particular health politic: “responsible freedom”. However, during a period of four months with high vaccination rate in 2021, the country exhibited the worst levels of disease Worldwide, applying the same politic.