Vaccination against COVID-19 has raised a series of questions related to the duration of immunity, the effectiveness of vaccines and how seroconversion of immunized patients is related to clinical outcomes, finding less evidence of biologicals that, like Coronovac. We seek to evaluate the effectiveness of the Sinovac vaccine against COVID-19, in terms of seroconversion and clinical follow-up in people over 70 years of age. A cohort follow-up study was designed with 411 patients older than 70 years vaccinated with Sinovac, who were tested for antibodies (protein S and N) after 28 days of completing the complete scheme with two doses. Additionally, clinical follow-up is being carried out, where variables such as adverse reactions associated with vaccination, possible COVID-19 infections after vaccination, admissions to hospitalization associated with the virus, including deaths, were included. Initially, the Elisa test was validated by determining levels of positive antibodies and their cut-off point. Regarding the symptoms associated with vaccination, it was identified that the most frequent was pain at the injection site. The positivity of the antibodies in the general group was 88.8%, showing a better response in women. There is evidence of a very low incidence of COVID-19 infection after having received the two doses of the vaccine (2.19%). No patient has been hospitalized or has died from any cause associated with COVID-19. The included patients developed neutralizing Ab between 84 and 92% of the cases. It should be noted that the immunogenicity studies with SINOVAC report between 50 and 90% generation of Ab.