RESUMEN
The Omicron variant is associated with increased transmissibility, but evidence about the impact of Omicron in seropositivity of children is limited. This study aims to evaluate SARS-CoV-2 seroprevalence in children during the different variants' subperiods. A prospective multicenter seroprevalence study was conducted in 7 University public hospitals in Greece from November 2021 to August 2022 (3 subperiods: November 2021-February 2022, March 2022-May 2022, June 2022-August 2022). Children from different age groups, admitted to the hospital or examined in outpatient clinics for reasons other than COVID-19 were enrolled. Neutralizing antibodies (Nabs), anti-Spike (anti-S) and anti-nucleocapsid (anti-N) SARS-CoV-2 IgG in serum were evaluated. A total of 2127 children (males:57,2%; median age:4,8years) were enrolled. Anti-N IgG seropositivity increased from 17,8% in the first sub-period to 40,7% in the second sub-period and then decreased in the third sub-period (36,7%). Anti-S IgG seropositivity appeared to have an increasing trend over the study period, starting from 34,8% and reaching 80,7%. Children aged 1-4 years old have significantly higher anti-N IgG titers compared to children aged 0-1 years old (p < 0,001). Infants have significantly lower anti-S IgG titers compared to all other age groups (p < 0,001). Immunocompromised children and infants have the lowest seropositivity for NAbs.Conclusions During the Omicron period, seropositivity significantly increased, as a result of higher transmissibility. Neonates and infants have lower antibody titers compared to other age groups, while young children aged 1-4 years old present higher antibody titers, suggesting that this age group may mount a higher antibody response. Continuous surveillance seroprevalence studies are needed in children, in order to identify the true extent of SARS-CoV-2 and guide the planning of adequate public health measures.
WHAT IS KNOWN: ⢠Seroprevalence surveys among children may be extremely useful, in order to properly monitor the immunity, either natural or acquired, through the quantification of IgG antibodies and to plan further immunization policies. ⢠There are variations in the seroprevalence of COVID-19 between the different periods, according to the vaccination rates, the type of circulating variant and the transmissibility of the virus. ⢠The Omicron variant is associated with increased transmissibility, but evidence about the impact of Omicron in seropositivity of children is limited. WHAT IS NEW: ⢠In this large multicenter seroepidemiological study, SARS-CoV-2 seroprevalence rate in children is higher during the Omicron period in comparison to the previous pandemic waves, due to the high transmissibility of the virus and the increased rates of reinfection. ⢠Neonates and infants have lower antibody titers compared to other age groups, while young children aged 14 years old present higher antibody titers, indicating that the children of this age group mount a higher antibody response. ⢠This study provides essential information about immunity and the level of protection in the pediatric population, as neutralizing antibodies were evaluated, in addition to the anti-N and anti-S IgG antibodies.
Asunto(s)
Anticuerpos Antivirales , COVID-19 , SARS-CoV-2 , Humanos , COVID-19/epidemiología , COVID-19/inmunología , Grecia/epidemiología , Estudios Seroepidemiológicos , Preescolar , SARS-CoV-2/inmunología , Masculino , Femenino , Niño , Estudios Prospectivos , Lactante , Anticuerpos Antivirales/sangre , Adolescente , Inmunoglobulina G/sangre , Anticuerpos Neutralizantes/sangre , Recién Nacido , Prueba Serológica para COVID-19RESUMEN
BACKGROUND: COVID-19 vaccination has been recommended for children to protect them and to enable in-person educational and social activities. METHODS: We estimated COVID-19 vaccination effectiveness (VE) against school absenteeism in children 5-17 years old hospitalized from September 1, 2021 through May 31, 2023. Full vaccination was defined as two vaccine doses. RESULTS: We studied 231 children admitted to hospital with COVID-19, including 206 (89.2 %) unvaccinated/partially vaccinated and 25 (10.8 %) fully vaccinated. Unvaccinated/partially vaccinated children were absent from school for longer periods compared to fully vaccinated children (median absence: 14 versus 10 days; p-value = 0.05). Multivariable regression showed that full COVID-19 vaccination was associated with fewer days of absence compared to no/partial vaccination on average (adjusted relative risk: 0.77; 95 % CI: 0.61 to 0.98). COVID-19 VE was 50.7 % (95 % CI: -11.3 % to 78.2 %) for school absenteeism above the median duration of absenteeism. CONCLUSIONS: Full COVID-19 vaccination conferred protection against school absenteeism in hospitalized school-aged children with COVID-19.