Abstract:Objective To study the effect of pertussis vaccination on the clinical manifestations of infants and young children with pertussis.Methods A retrospective analysis was performed to investigate the differences in clinical manifestations and peripheral blood cell levels between pertussis children with different pertussis vaccination status.Results A total of 1083 children with pertussisat at age of<3 years were enrolled,with 551 children in the unvaccinated group and 532 in the vaccinated group.Of all the children,392 had an age of onset of<3 months(372 were unvaccinated and 20 were vaccinated)and 691 children had an age of onset of≥3 months(179 were unvaccinated and 512 were vaccinated).Compared with the vaccinated group,the unvaccinated group had a longer length of hospital stay and a higher incidence rate of respiratory failure(P<0.05).Among the children≥3 months of age,the incidence of severe pneumonia in the unvaccinated group was higher than that in the vaccinated group(P<0.05),and the incidence of severe pneumonia was the highest in the unvaccinated group(10.6%)and the lowest in the 4-dose vaccination group(1.2%).Among the 101 patients with severe pneumonia,80(79.2%)were observed in the unvaccinated group and only 21(20.8%)in the four different doses vaccination groups.For the children with an age of onset of≥3 months,the unvaccinated group had higher white blood cell count,absolute value of lymphocytes,and platelet count than the vaccinated group(P<0.05).Conclusions Pertussis vaccination can reduce the incidence of severe pneumonia and respiratory failure and alleviate the severity of respiratory complications in infants and young children with pertussis.