Vaccinated individuals who presented with symptoms and signs of severe COVID-19 disease or death at least 14 days after receiving their second dose of the CoronaVac vaccine in the state of Roraima were investigated. Data collection included reviewing databases of the Influenza Epidemiological Surveillance Information System, National Immunization Program, and public and private hospitals. Data was linked across the databases to identify possible cases . Nine probable cases of vaccine failure were identified. These individuals were further described in a case series, which showed that all had pre-existing comorbidities and/or were above 60 years of age. In addition, the researchers found that obesity was a statistically significant risk factor influencing the severity of COVID-19 infection.
Ultimately, EpiSUS fellows found a total vaccine effectiveness rate of 97.74 percent when looking at the number of probable cases of vaccine failure (n=9) as a proportion of the population with a complete vaccination schedule. Fellows also conducted an evaluation of the knowledge and practices of individuals administering vaccines, identifying a number of areas for improvement, including record keeping, screening of patient symptoms before vaccination, and monitoring vaccine temperature during storage. As a result, fellows recommended that local health authorities provide training on immunization best practices to local health professionals including nurses and technicians.
Despite the challenges involved in investigating vaccine-related issues, it was possible to identify that vaccine effectiveness was within the expected parameters, and that individual factors such as obesity and older age may have been related to the negative outcomes. These findings were critical to help fight the rumor, regain trust in the health system, and boost the national immunization campaign.