A Single BNT162b2 Dose Protects Against SARS-CoV-2: A Case Report of a Family Cluster of COVID-19.

Background. Coronavirus 2019 (COVID-19) disease is an infectious disease caused by the virus "Severe Acute Respiratory Syndrome Coronavirus 2" (SARS-CoV-2). This virus generated a pandemic in 2020 and has affected millions of people worldwide. Facing the need to prevent its contagion, the vaccine BNT162b2 was approved in December 2020 in Mexico and started administered in healthcare workers. Case presentation. We presented here, two healthcare workers vaccinated with one single dose of BNT162b2, who lives in a family nucleus with high transmission rate of SARS-CoV-2. These healthcare workers, identified in the manuscript as patient E and F, were asymptomatic and their real-time RT-PCR test for SARS-CoV-2 resulted negative, while the rest of the family (patients A-D) were SARS-CoV-2 positive. The antibody titers IgG anti-spike of patient F (after the second dose; 1080 Au/mL) turned out greater than patient E (before the second dose; 37.1 Au/mL). Discussion. To our knowledge this is the first case report of the protective effect of single BNT162b2 vaccine dose in the context of high transmission rates within a family nucleus. Despite changes induced by BNT162b2 in the antibody titers with single or double dose vaccination, a single dose of BNT162b2 showed to be sufficient for immunization of patients against COVID-19.