The Covid-19 vaccines currently distributed by the National Immunization Program (NIP)
have undergone a rigorous safety and efficacy assessment by the National Surveillance
Agency Sanitary prior to the authorization of use in the country. The main objective of
vaccination against Covid19 is to reduce its morbidity and mortality and, in the future,
to promote the control of transmission from the prevention of symptomatic cases in the
general population.

To achieve this goal, however, it is important that the vaccines are administered
correctly (according to the vaccination schedule correct application techniques and
appropriate storage conditions, for example), in the selected population groups
(according to prioritization criteria), with vaccination coverage and selected population
groups (according to prioritization criteria), with vaccination coverage and vaccination
speeds sufficient for effective control of the disease.That is, there are factors that
extrapolate the issues of quality, efficacy and safety evaluated in the pre-registration
stages, which are extremely important for the success of immunization programs. Thus, the
monitoring of these parameters after large-scale use is essential to ratify the favorable
risk-benefit assessment made at the time of decision on the introduction of these
vaccines in the NIP.

Regarding the role of vaccines in the prevention and control of target diseases, in
addition to data from efficacy and immunogenicity obtained in the controlled situations
of clinical trials, it is necessary to extend this assessment to routine situations,
i.e., "real life", based on the so-called effectiveness studies. Factors such as storage
and administration conditions of these products, issues related to vaccinated populations
and individuals may affect the response to vaccines.

Therefore, the monitoring of effectiveness must be continuous, seeking to prove the
impact of the vaccines in reducing the occurrence of the disease, as well as generating
vaccine immunogenicity data, which can be used in the future as protective inferences in
complementary analyses.

Thus, the present research project is a study of the effectiveness of the vaccination
whereas the efficacy of licensed vaccines, demonstrated in controlled studies, that needs
to be verified in the routine of immunization services throughout the country, with its
diversity including different vaccination coverage and circulation of SARS-CoV-2
variants, as well as individual factors, such as age group and presence of comorbidities.

The performance of immunization in susceptible population generates groups exposed and
not exposed to the COVID-19 vaccine.

Underlying hypothetical cohorts of vaccinated and unvaccinated cannot be clearly
enumerated, and the strategy is to reconstruct the experience of exposure (vaccination)
and disease (COVID-19) in this population.

In addition to efficacy data obtained from pre-licensing/authorisation clinical trials
and the monitoring of vaccine effectiveness, the main objective of this study, to obtain
data on the development of immune response to symptomatic SARS-CoV-2 infection (COVID-19)
is of great importance for future immunization actions, especially, the development of
future vaccines. In the near future, with the increasing availability of vaccines
COVID-19, it will become increasingly difficult (for ethical and programmatic reasons) to
conduct trials placebo-controlled clinical trials, which may be replaced by
immunogenicity studies.

However, for this, it will be necessary to improve knowledge in relation to the
post-infection immune response and also that triggered by vaccination, moving towards the
definition of the so-called correlates of serum protection.

In this context, we included in the present case-control study proposal, the
establishment of a cohort of cases and controls, grouped according to vaccination history
for COVID-19, for follow-up and evaluation of your humoral and cellular immune response.

We understand be an opportunity, based on the identification of virologically confirmed
cases and a control with SARS-CoV-2 infection known to be ruled out, observe and describe
the humoral and cellular immune response components in these research participants,
including duration immunity for a period of 12 months.