BACKGROUND: A serosurvey to evaluate population immunity to polioviruses (PVs) in the context of the importation-related wild PV1 outbreak in Tajikistan in 2010 (461 confirmed cases among children and young adults) was conducted. METHODS: Serum specimens from a nationwide sample of 1-24 year-old persons selected through stratified cluster sampling (n=2447) were tested for neutralizing antibodies to all three PV types. Samples with titers<1:8 were considered seronegative. The serosurvey was conducted during the interval after mOPV1 supplementary immunization activities (SIAs) and before tOPV SIAs (targeting ages ≤ 15 years) implemented to control the outbreak. In the absence of pre-outbreak specimens, results for PV3 were used as a proxy for pre-outbreak PV1 immunity patterns. RESULTS: Overall, PV1 seroprevalence was 98.9%, PV2 seroprevalence was 98.8%, and PV3 seroprevalence was 86.9%. PV1 and PV2 seroprevalence exceeded 95% in all age groups and regions. PV3 seroprevalence was <90% in all age groups and regions, except 15-19 year-olds (91.7%) and Dushanbe (90.0%). PV3 seroprevalence was lowest among 1-4 (82.7%) and 5-9 (84.4%) year-olds, particularly among 1-4 year-olds in Kurgan-Tube (76.3%) and RRS (80.0%) regions. Birth cohorts immunized only through routine services (ages, 1-7 years) had lower PV3 seroprevalence than birth cohorts targeted by the SIAs during 1995-2002 (8-19 years): 82.5% versus 89.3%, p<0.001. CONCLUSIONS: Suboptimal (<90%) PV3 seroprevalence across wide age range suggests the outbreak resulted from accumulation of susceptibles due to suboptimal coverage over a long time period, particularly in the birth cohorts immunized only through routine services and in areas where the outbreak began (Kurgan-Tube and RRS). High PV1 seroprevalence indicates that mOPV1 SIAs with expanded target age (≤ 15 years) succeeded in closing the immunity gap and ongoing WPV1 transmission is unlikely. To accelerate outbreak control in areas which have been polio-free for long time, expanding SIA target age should be considered.
BACKGROUND: A serosurvey to evaluate population immunity to polioviruses (PVs) in the context of the importation-related wild PV1 outbreak in Tajikistan in 2010 (461 confirmed cases among children and young adults) was conducted. METHODS: Serum specimens from a nationwide sample of 1-24 year-old persons selected through stratified cluster sampling (n=2447) were tested for neutralizing antibodies to all three PV types. Samples with titers<1:8 were considered seronegative. The serosurvey was conducted during the interval after mOPV1 supplementary immunization activities (SIAs) and before tOPV SIAs (targeting ages ≤ 15 years) implemented to control the outbreak. In the absence of pre-outbreak specimens, results for PV3 were used as a proxy for pre-outbreak PV1 immunity patterns. RESULTS: Overall, PV1 seroprevalence was 98.9%, PV2 seroprevalence was 98.8%, and PV3 seroprevalence was 86.9%. PV1 and PV2 seroprevalence exceeded 95% in all age groups and regions. PV3 seroprevalence was <90% in all age groups and regions, except 15-19 year-olds (91.7%) and Dushanbe (90.0%). PV3 seroprevalence was lowest among 1-4 (82.7%) and 5-9 (84.4%) year-olds, particularly among 1-4 year-olds in Kurgan-Tube (76.3%) and RRS (80.0%) regions. Birth cohorts immunized only through routine services (ages, 1-7 years) had lower PV3 seroprevalence than birth cohorts targeted by the SIAs during 1995-2002 (8-19 years): 82.5% versus 89.3%, p<0.001. CONCLUSIONS: Suboptimal (<90%) PV3 seroprevalence across wide age range suggests the outbreak resulted from accumulation of susceptibles due to suboptimal coverage over a long time period, particularly in the birth cohorts immunized only through routine services and in areas where the outbreak began (Kurgan-Tube and RRS). High PV1 seroprevalence indicates that mOPV1 SIAs with expanded target age (≤ 15 years) succeeded in closing the immunity gap and ongoing WPV1 transmission is unlikely. To accelerate outbreak control in areas which have been polio-free for long time, expanding SIA target age should be considered.
Authors: B Mao; K Chheng; K Wannemuehler; E Vynnycky; S Buth; S C Soeung; S Reef; W Weldon; L Quick; C J Gregory Journal: Epidemiol Infect Date: 2014-11-06 Impact factor: 4.434
Authors: Concepcion F Estivariz; Sarah D Bennett; Jacquelyn S Lickness; Leora R Feldstein; William C Weldon; Eva Leidman; Daniel C Ehlman; Muhammad F H Khan; Jucy M Adhikari; Mainul Hasan; Mallick M Billah; M Steven Oberste; A S M Alamgir; Meerjady D Flora Journal: PLoS Med Date: 2020-03-31 Impact factor: 11.069