Objective:To evaluate the effects of vaccine switch on the levels of neutralizing antibody (NA) of poliovirus in children aged<12 years.Methods:Subjects aged<12 years from 9 districts in Fujian province were chosen by stratified cluster and complete random sampling method. Blood samples were collected for testing NA of poliovirus by microcell neutralization.Results:A total of 2 134 subjects aged<12 years were selected. The positive rate of NA against PVⅠand Ⅲ were 98.64% and 95.83%; and geometric mean titers (GMTs) were 1∶259.35 and 1∶105.14, respectively. The GMTs presented a trend of decreasing as age increased. Compared to trivalent oral poliovirus vaccine (tOPV), bivalent oral poliovirus vaccine (bOPV) and inactivated poliovirus vaccine (IPV) induced higher GMTs of NA against poliovirusⅠand Ⅲ respectively. Among 182 children aged<5 years, the positive rate of NA against PVⅠ, Ⅱ, Ⅲ were 97.25%, 76.37% and 92.86%. There were statistical differences among the three types ( χ2=44.44, P=0.000). The rate of NA against PVⅡwas significantly lower than those ofⅠand Ⅲ (Ⅱ vs. I: χ2=34.65, P=0.000; Ⅱ vs. Ⅲ: χ2=18.99, P=0.000). And the GMTs of NA against PV Ⅰ, Ⅱ, Ⅲ were 1∶368.96、1∶23.06 and 1∶183.10, which were significantly different ( F=156.54, P=0.000). The GMT of PVⅠwas the highest, PV Ⅲ was the second, PVⅡ was lowest (pairwise comparison showed values of P all were 0.000). The analysis of general linear model showed that the interval between the date of last immunization and the date of sample collection would affect the GMTs of PVⅠand Ⅲ, different vaccine models would affect only the GMT of PV Ⅰ. The age maybe was a confounding factor. But no factors would affect the GMT of PV Ⅱ. Conclusions:After the vaccine switch, the level of NA against PVⅠand PV Ⅲ were still maintaining high level, but the level of PVⅡamong children<5 years was at relatively low level, which indicated that the surveillance should be strengthened.

Objective:To analyze the prevalence of different genotypes of wild measles virus in Fujian province from 2014 to 2019.Methods:The information of suspected measles cases and the throat swab specimens of the cases in Fujian province from 2014 to 2019 were collected. Reverse transcription-polymerase chain reaction was applied to amplify the 450 nucleotides of the 3-terminal of the nucleoprotein gene. Phylogenetic tree was constructed to identify and analyze the target sequence.Results:A total of 1 102 suspected measles cases were reported in Fujian province from 2014 to 2019, with an annual incidence rate of 0.47/100 000. Totally 884 throat swabs were tested in the laboratory, and 179 nucleotide sequences were obtained except vaccine strain. Sequence analysis showed that 110 measles genotypes were H1, 43 were B3 and 26 were D8. Nucleotide homology analysis showed that the H1a genotype measles virus in Fujian province distributed in two branches, divided into nine different sequence variants. Some of the variants were highly homologous (99.8%-100.0%) with the measles strains in other regions and countries. There were six different sequence variants of B3 genotype measles virus in Fujian province. The nucleotide homology between the B3 genotype measles virus in Fujian province and the domestic and foreign prevalent B3 strains was 98.4%-100.0%. The D8 genotype measles strain in Fujian province had five different sequence variants, some of which were highly homologous with the strains from Vietnam, Japan and Thailand.Conclusions:Three different genotypes of measles viruses (H1, B3 and D8) prevailed in Fujian province from 2014 to 2019, among which H1 genotype was still the local endemic genotype, while B3 and D8 genotypes were imported genotypes in Fujian province. The result indicated that although the local cases of measles were less in Fujian province in recent years, the risk of imported cases from abroad was increasing, and the surveillance of imported cases from abroad should be strengthened.