RESUMO
Objective:To investigate the serum antibody level in children with pertussis in Hangzhou city, and to evaluate the incidence of pertussis in children and the immunization effect of vaccine.Methods:A retrospective study was conducted.The pertussis toxin IgG antibody levels in 1 486 children aged 0-14 who received physical exa-mination in Hangzhou Children′s Hospital from January to December 2018 of were collected and analyzed.Serum antibody level ≥30 IU/mL was considered seropositive.The children enrolled were divided into the 0-3-year-old, 4-6-year-old, 7-9-year-old and 10-14-year-old groups; then the children under 3 years old were subdivided into groups of 0-<3 months, 3-<6 months, 6-<9 months, 9-<12 months, 12-<18 months, and 18-≤ 36 months; finally, the children were grouped according to their vaccination times, the pertussis toxin IgG antibody level and the infection rate of pertussis were compared among different groups by Mann- Whitney U, Kruskal- Wallis and χ2 tests. Results:The overall positive rate of the pertussis toxin IgG antibody was 23.62% (351/1 486), and the median antibody concentration was 6.60 IU/mL.Among children aged 0-14, the 0-3-year-old children had the highest positive rate of the pertussis toxin IgG antibody and the highest median antibody concentration, which were 24.58% (29/118) and 6.95 IU/mL, respectively.There was no significant difference in the antibody positive rate and the median antibody concentration among different age groups (all P>0.05). Among different subgroups of children aged 0-3, the pertussis toxin IgG antibody positive rate and the median antibody concentration were statistically significant (all P<0.05). It was predicted that the pertussis infection rate in children over 3 years old in Hangzhou was about 45.99%.The patients receiving more than 3 doses of vaccination accounted for 87.48% (1 300/1 486), and their antibody positive rate was 25.46% (331/1 300). After excluding unvaccinated children, the comparison results suggested that there was statistical significance in the antibody positive rate and median antibody concentration among different vaccination groups ( χ2=24.467, 67.438, all P<0.001). Conclusions:The serum pertussis toxin IgG antibody positive rate in children aged 0-14 in Hangzhou is low, but their predicted pertussis infection rate is higher.Children aged 0-14 are easy to become a main source of infection.Therefore, it is necessary to pay attention to and strengthen the vaccination plan and research, enhance the monitoring of the infection source, and prevent the " recurrence of pertussis" .
RESUMO
BackgroundThe ongoing outbreak of novel corona virus disease 2019 (COVID-19) in Wuhan, China, is arousing international concern. This study evaluated whether and when the infected but asymptomatic cases during the incubation period could infect others. MethodsWe collected data on demographic characteristics, exposure history, and symptom onset day of the confirmed cases, which had been announced by the Chinese local authorities. We evaluated the potential of transmission during the incubation period in 50 infection clusters, including 124 cases. All the secondary cases had a history of contact with their first-generation cases prior to symptom onset. ResultsThe estimated mean incubation period for COVID-19 was 4.9 days (95% confidence interval [CI], 4.4 to 5.4) days, ranging from 0.8 to 11.1 days (2.5th to 97.5th percentile). The observed mean and standard deviation (SD) of serial interval was 4.1{+/-}3.3 days, with the 2.5th and 97.5th percentiles at -1 and 13 days. The infectious curve showed that in 73.0% of the secondary cases, their date of getting infected was before symptom onset of the first-generation cases, particularly in the last three days of the incubation period. ConclusionsThe results indicated the transmission of COVID-9 occurs among close contacts during the incubation period, which may lead to a quarantine loophole. Strong and effective countermeasures should be implemented to prevent or mitigate asymptomatic transmission during the incubation period in populations at high risk.