-
From October 2012 through March 2014, 28 cases of VAPP were reported in the 8 PLADs. Of the 28 cases, 12 were laboratory-confirmed VAPP — 10 recipient cases and 2 contact cases — and the remaining 16 cases were recipient, clinically-compatible cases (Table 1). Figure 1 showed the distribution of VAPP cases by time and laboratory confirmation status.
PLAD No. of cases Laboratory-confirmed VAPP Clinically-compatible VAPP Recipient Contact Subtotal Recipient Contact Subtotal Hebei 4 2 0 2 2 0 2 Jiangsu 2 0 0 0 2 0 2 Shandong 8 4 0 4 4 0 4 Henan 6 2 0 2 4 0 4 Hubei 1 1 0 1 0 0 0 Guangdong 3 0 1 1 2 0 2 Guangxi 2 1 1 2 0 0 0 Sichuan 2 0 0 0 2 0 2 Total 28 10 2 12 16 0 16 Table 1. Vaccine-associated paralytic poliomyelitis (VAPP) cases in 8 provincial-level administrative divisions (PLADs) of China between October 2012 and March 2014.
Figure 1.Time distribution of paralysis onset for the 28 Vaccine-associated paralytic poliomyelitis (VAPP) cases.
All VAPP cases were among children less than 2 years of age. The other 26 cases were among infants, including 8 cases at 2 months, 14 at 3 months, 1 at 4 months, and 1 at 5 months of age (Figure 2).
Figure 2.Age distribution of the 28 VAPP cases and other AFP cases with and without residual paralysis with onset by 30 months of age. Abbreviations: VAPP=Vaccine-associated paralytic poliomyelitis; AFP=Acute flaccid paralysis.
Of the 28 cases, 27 were among males (χ2=15.7464, p<0.0001). Single-factor logistic regression analysis showed that the male∶female ratio was significantly greater than one (male∶female odds ratio=18.97, 95%CI: 2.56–140.78).
Of the 28 cases, 26 were among OPV recipients with 10 being laboratory-confirmed and 16 being clinically-compatible cases. Among OPV-recipient cases, 22 (84.6%) occurred following the first dose of OPV, and the median length of time between receiving the OPV and onset of paralysis was 21.5 days (range: 12–32 days). Furthermore, 3 (11.5%) cases occurred following the second dose of OPV, with onsets of paralysis at 17, 31, and 35 days after receiving the OPV. The other recipient VAPP case had a history of previous vaccination with 2 doses of OPV, with time windows of 10 days from the second dose and 38 days from the first dose, both doses being within the interval of 6–40 days.
Among the 12 laboratory-confirmed cases, PV1 was isolated from 2 cases, PV2 from 3 cases, PV3 from 2 cases, PV1+3 from 2 cases, PV2+3 from 1 case, and all three types from 2 cases. PV2 and PV2+3 polioviruses were isolated from the 2 contact laboratory-confirmed VAPP cases.
The 8 PLADs had a 11.36 million births during the study period yielding an estimated incidence of 2.47 cases per million (95%CI: 1.64–3.56 per million) from the 28 cases. The estimated incidence of VAPP per PLAD ranged from 1.05 to 4.74 cases per million births (Figure 3), with Shandong having the highest incidence and Hubei having the lowest incidence. Differences by PLAD were not statistically significant.
Figure 3.Estimated incidence of VAPP in 8 PLADs using numbers of births between October 2012 and March 2014 as denominators. Abbreviations: VAPP=Vaccine-associated paralytic poliomyelitis; PLADs=provincial-level administrative divisions.
A total of 50.52 million doses of OPV were administered from October 2012 to March 2014, yielding an estimated VAPP incidence of 0.55 cases per million routine OPV doses (95%CI: 0.37–0.80 cases per million doses) due to the 28 cases. The estimated incidence for each of the 8 PLADs ranged from 0.26 to 1.35 cases per million (Figure 4), with Shandong ranking the highest and Hubei the lowest among the 8 PLADs. Differences by PLAD were not statistically significantly different. When OPV administered during SIAs was included in the denominator, the overall incidence of VAPP was 0.28 cases per million doses (Table 2).
Figure 4.Estimated incidences of VAPP per routinely-administered dose of OPV in 8 PLADs during the study period. Abbreviations: VAPP=Vaccine-associated paralytic poliomyelitis; PLADs=provincial-level administrative divisions.
Provisnce VAPP Lab confirmed VAPP Clinical compatible VAPP No. of cases Estimated incidence (95%CI) No. of cases Eestimated incidence (95%CI) No. of cases Estimated incidence (95%CI) Using number of births as the denominator Hebei 4 2.83(0.71–7.21) 2 1.41(0.14–5.09) 2 1.41(0.14–5.09) Jiangsu 2 1.79(0.18–6.43) 0 0.00(0.00–3.30) 2 1.79(0.18–6.43) Shandong 8 4.74(2.01–9.36) 4 2.37(0.59–6.04) 4 2.37(0.59–6.04) Henan 6 3.20(1.17–6.99) 2 1.07(0.11–3.84) 4 2.13(0.53–5.44) Hubei 1 1.05(0.11–5.88) 1 1.05(0.11–5.88) 0 0.00(0.00–3.89) Guangdong 3 1.63(0.33–4.79) 1 0.54(0.05–3.00) 2 1.09(0.11–3.92) Guangxi 2 1.78(0.18–6.40) 2 1.78(0.18–6.40) 0 0.00(0.00–3.29) Sichuan 2 1.62(0.15–5.34) 0 0.00(0.00–2.74) 2 1.48(0.15–5.34) Total 28 2.47(1.64–3.56) 12 1.06(0.55–1.85) 16 1.41(0.83–2.99) Using number of routine OPV doses administered as the denominator Hebei 4 0.60(0.15–1.54) 2 0.30(0.03–1.08) 2 0.30(0.03–1.08) Jiangsu 2 0.34(0.03–1.23) 0 0.00(0.00–0.63) 2 0.34(0.03–1.23) Shandong 8 1.35(0.57–2.67) 4 0.68(0.17–1.72) 4 0.68(0.17–1.72) Henan 6 0.60(0.22–1.30) 2 0.20(0.02–0.72) 4 0.40(0.10–1.01) Hubei 1 0.26(0.03–1.48) 1 0.26(0.03–1.48) 0 0.00(0.00–0.97) Guangdong 3 0.35(0.07–1.02) 1 0.12(0.01–0.65) 2 0.23(0.02–0.84) Guangxi 2 0.40(0.04–1.43) 2 0.40(0.04–1.43) 0 0.00(0.00–0.73) Sichuan 2 0.43(0.04–1.56) 0 0.00(0.00–0.80) 2 0.43(0.04–1.56) Total 28 0.55(0.37–0.80) 12 0.24(0.12–0.42) 16 0.32(0.19–0.51) Using number of routine and SIA campaigns OPV doses administered as the denominator Hebei 4 0.19(0.05–0.47) 2 0.09(0.01–0.33) 2 0.09(0.04–0.33) Jiangsu 2 0.32(0.03–1.14) 0 0.00(0.00–0.58) 2 0.32(0.03–1.14) Shandong 8 0.46(0.2–0.91) 4 0.23(0.06–0.59) 4 0.23(0.06–0.59) Henan 6 0.29(0.11–0.64) 2 0.10(0.01–0.35) 4 0.19(0.05–0.50) Hubei 1 0.18(0.02–0.99) 1 0.18(0.02–0.99) 0 0.00(0.00–0.65) Guangdong 3 0.22(0.04–0.65) 1 0.07(0.01–0.41) 2 0.15(0.01–0.53) Guangxi 2 0.24(0.02–0.88) 2 0.01(0.02–0.88) 0 0.00(0.00–0.45) Sichuan 2 0.27(0.03–0.95) 0 0.00(0.00–0.49) 2 0.27(0.03–0.95) Total 28 0.28(0.18–0.40) 12 0.12(0.06–0.21) 16 0.16(0.09–0.26) Abbreviations: VAPP=vaccine-associated paralytic poliomyelitis; OPV=oral poliovirus vaccine; SIA=supplementary immunization activities. Table 2. Estimated incidences of VAPP, lab confirmed VAPP, and clinically-compatible VAPP (using number of births and number of routine OPV doses administered as denominators).
Using the number of routine OPV1 doses administered as the denominator, the VAPP incidence following the first dose was 1.61 cases per million (95%CI: 1.01–2.43 cases per million). Using the number of routine OPV2 doses administered as a denominator, the VAPP incidence following the second dose was 0.23 cases per million (95%CI: 0.05–0.67 cases per million) (Table 3). The relative risk of VAPP following the first OPV dose compared with the second OPV dose was 7.07 (95%CI: 2.12–23.62).
Province Following first dose Following second dose No. of cases Estimated incidence (95%CI) No. of cases Estimated incidence (95%CI) Hebei 2 1.15(0.11–4.13) 2 1.13(0.11–4.06) Jiangsu 1 0.65(0.07–3.66) 0 0.00(0.00–2.42) Shandong 8 5.26(2.23–10.38) 0 0.00(0.00–2.39) Henan 5 1.94(0.62–4.54) 1 0.39(0.04–2.21) Hubei 1 0.85(0.09–4.77) 0 0.00(0.00–3.76) Guangdong 2 0.73(0.07–2.63) 0 0.00(0.00–1.57) Guangxi 1 0.75(0.08–4.22) 0 0.00(0.00–2.88) Sichuan 2 1.87(0.19–6.75) 0 0.00(0.00–3.15) Total 22 1.61(1.01–2.43) 3 0.23(0.05–0.67) Abbreviations: VAPP=vaccine-associated paralytic poliomyelitis; CI=confidence intervals. Table 3. Estimated incidences of VAPP per million following the first and the second dose of oral poliovirus vaccine by provincial-level administrative division.
HTML
Citation: |