ABSTRACT Twenty-seven children aged seven months to 5 years were inadvertently vaccinated with a COVID-19 vaccine, the CoronaVac (Sinovac, China), an inactivated SARS-CoV-2 vaccine, in two different cities of Sao Paulo State, Brazil. After the event, these children were monitored by local pediatricians and serum samples were collected at the first visit and 30 days after vaccination and tested for SARS-CoV-2 S1 serology with Ortho total IgG anti-S1 protein and Cpass, an ACE2 receptor binding domain inhibition assay. Only one child had a mild symptom after vaccination, with no other adverse events documented up to the 30 days follow-up. Of 27 children tested 3-9 days after vaccination, 5 (19%) had positive serology suggesting a previous natural SARS-CoV-2 infection, with all 19 tested on day 30 after vaccination and presenting with positive tests, with an increment of antibody titers in those initially positive. A low Cpass binding inhibition was observed in the first collection in 11 seronegative cases, with high titers among those anti-S1 positive. All children showed an important increase in antibody titers on day 30. The event allowed the documentation of a robust serological response to one dose of CoronaVac in this small population of young children, with no major adverse effects. Although it was an unfortunate accident, this event may contribute with future vaccine strategies in this age group. The data suggest that CoronaVac is safe and immunogenic for children.

Resumo Objetivo: descrever a ocorrência da hepatite B entre gestantes, a realização de imunoprofilaxia e a transmissão vertical e perinatal nas crianças expostas ao vírus na rede de Atenção Primária à Saúde do estado de São Paulo, Brasil. Métodos: estudo transversal sobre registros de pré-natal de gestantes atendidas de janeiro a junho de 2012 e coorte dos recém-nascidos; foram descritas as frequências dos resultados e calculada a estimativa da ocorrência da hepatite B. Resultados: foram incluídas 6.233 gestantes, das quais 53,1% com 20 a 29 anos de idade, 58,7% com 8 a 11 anos de estudo, 53,3% brancas e 73,9% com companheiro; a ocorrência de hepatite B foi de 0,13% (IC95%: 0,04 a 0,21%); das oito crianças de mães com hepatite B crônica, seis tiveram esquema vacinal completo e não houve transmissão vertical ou perinatal. Conclusão: observou-se baixa ocorrência de hepatite B em gestantes e ausência de transmissão vertical ou perinatal.

Abstract Objective: to describe the occurrence of hepatitis B among pregnant women, immunoprophylaxis and vertical and perinatal transmission in children exposed to the virus in the São Paulo state primary care network, Brazil. Methods: this was a cross-sectional study using prenatal records of pregnant women attending health services between January and June 2012 and a cohort of newborns; the frequencies of the results were described and the estimated occurrence of hepatitis B was calculated. Results: 6,233 pregnant women were included, of whom 53.1% were between 20-29 years old, 58.7% had 8-11 years of schooling, 53.3% were white, and 73.9% lived with a partner; occurrence of hepatitis B was 0.13% (95%CI 0.04; 0.21); of the eight children of mothers with chronic hepatitis B, six had a complete vaccination schedule, and there was no vertical or perinatal transmission. Conclusion: there was low occurrence of hepatitis B in pregnant women and absence of vertical or perinatal transmission.

Resumen Objetivo: describir el aparecimiento de hepatitis B en mujeres embarazadas, la inmunoprofilaxis y la transmisión vertical y perinatal en niños expuestos al virus en la red de atención primaria en el estado de São Paulo, Brasil. Métodos: estudio transversal con registros prenatales de mujeres embarazadas atendidas de enero a junio de 2012 y cohorte de recién nacidos; se describieron las frecuencias y se calculó el surgimiento de la hepatitis B. Resultados: se incluyeron 6.233 gestantes, de las cuales 53,1% con 20 a 29 años de edad, 58,7% con 8 a 11 años de estudios, 53,3% blancas y 73,9% viviendo en pareja; la ocurrencia de hepatitis B fue del 0,13% (IC95%: 0,04 to 0,21%); entre ocho hijos de madres con hepatitis B crónica, seis tenía un calendario de vacunación completo y no había transmisión vertical o perinatal. Conclusión: hubo baja ocurrencia de hepatitis B en mujeres embarazadas y ausencia de transmisión vertical o perinatal.

Resumo Objetivo: descrever a ocorrência da hepatite B entre gestantes, a realização de imunoprofilaxia e a transmissão vertical e perinatal nas crianças expostas ao vírus na rede de Atenção Primária à Saúde do estado de São Paulo, Brasil. Métodos: estudo transversal sobre registros de pré-natal de gestantes atendidas de janeiro a junho de 2012 e coorte dos recém-nascidos; foram descritas as frequências dos resultados e calculada a estimativa da ocorrência da hepatite B. Resultados: foram incluídas 6.233 gestantes, das quais 53,1% com 20 a 29 anos de idade, 58,7% com 8 a 11 anos de estudo, 53,3% brancas e 73,9% com companheiro; a ocorrência de hepatite B foi de 0,13% (IC95%: 0,04 a 0,21%); das oito crianças de mães com hepatite B crônica, seis tiveram esquema vacinal completo e não houve transmissão vertical ou perinatal. Conclusão: observou-se baixa ocorrência de hepatite B em gestantes e ausência de transmissão vertical ou perinatal.

Abstract Objective: to describe the occurrence of hepatitis B among pregnant women, immunoprophylaxis and vertical and perinatal transmission in children exposed to the virus in the São Paulo state primary care network, Brazil. Methods: this was a cross-sectional study using prenatal records of pregnant women attending health services between January and June 2012 and a cohort of newborns; the frequencies of the results were described and the estimated occurrence of hepatitis B was calculated. Results: 6,233 pregnant women were included, of whom 53.1% were between 20-29 years old, 58.7% had 8-11 years of schooling, 53.3% were white, and 73.9% lived with a partner; occurrence of hepatitis B was 0.13% (95%CI 0.04; 0.21); of the eight children of mothers with chronic hepatitis B, six had a complete vaccination schedule, and there was no vertical or perinatal transmission. Conclusion: there was low occurrence of hepatitis B in pregnant women and absence of vertical or perinatal transmission.

Resumen Objetivo: describir el aparecimiento de hepatitis B en mujeres embarazadas, la inmunoprofilaxis y la transmisión vertical y perinatal en niños expuestos al virus en la red de atención primaria en el estado de São Paulo, Brasil. Métodos: estudio transversal con registros prenatales de mujeres embarazadas atendidas de enero a junio de 2012 y cohorte de recién nacidos; se describieron las frecuencias y se calculó el surgimiento de la hepatitis B. Resultados: se incluyeron 6.233 gestantes, de las cuales 53,1% con 20 a 29 años de edad, 58,7% con 8 a 11 años de estudios, 53,3% blancas y 73,9% viviendo en pareja; la ocurrencia de hepatitis B fue del 0,13% (IC95%: 0,04 to 0,21%); entre ocho hijos de madres con hepatitis B crónica, seis tenía un calendario de vacunación completo y no había transmisión vertical o perinatal. Conclusión: hubo baja ocurrencia de hepatitis B en mujeres embarazadas y ausencia de transmisión vertical o perinatal.