Effectiveness of rotavirus vaccine in preventing transmission of rotavirus from children to household contacts in Malawi

Abstract Horizontal transmission of rotavirus vaccine virus may contribute to indirect effects of rotavirus vaccine, but data are lacking from low-income countries. Serial stool samples were obtained from Malawian infants who received 2 doses of monovalent human rotavirus vaccine (RV1) (days 4, 6, 8, and 10 after vaccination) and from their household contacts (8–10 days after vaccine). RV1 vaccine virus in stool was detected using semiquantitative real-time reverse-transcription polymerase chain reaction. RV1 fecal shedding was detected in 41 of 60 vaccinated infants (68%) and in 2 of 147 household contacts (1.4%). Horizontal transmission of vaccine virus within households is unlikely to make a major contribution to RV1 indirect effects in Malawi.

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Community transmission of rotavirus infection in a vaccinated population in Malawi: a prospective household cohort study

10.1101/2020.04.05.20036574 ◽

2020 ◽

Author(s):

Aisleen Bennett ◽

Louisa Pollock ◽

Naor Bar-Zeev ◽

Joseph A. Lewnard ◽

Khuzwayo C. Jere ◽

...

Keyword(s):

Low Income ◽

Asymptomatic Infection ◽

Vaccine Effectiveness ◽

Low Income Countries ◽

Rotavirus Vaccine ◽

Rotavirus Infection ◽

Indirect Transmission ◽

Household Contacts ◽

Asymptomatic Children ◽

Increased Risk

AbstractBackgroundRotavirus vaccine effectiveness (VE) is reduced among children in low-income countries (LICs). Indirect (transmission-mediated) effects of rotavirus vaccine may contribute to the total population impact of vaccination. We estimated the effectiveness of rotavirus vaccine in preventing transmission of rotavirus to household contacts in Blantyre, Malawi.MethodsWe recruited vaccine-age-eligible children with acute rotavirus gastroenteritis (case-children), together with their household contacts. Clinical data and stool samples were collected from case-children at presentation, and prospectively from household contacts over 14 days. A single stool sample was collected from control households containing asymptomatic children age-matched to case-children. Samples were tested for rotavirus using real-time PCR. Risk factors for household transmission of rotavirus infection and clinical rotavirus disease were identified using logistic regression. Vaccine effectiveness against transmission (VET) was estimated as one minus the ratio of secondary attack rates (SAR) in vaccinated and unvaccinated populations, using VE estimates from the associated diarrhoeal surveillance platform to estimate the counterfactual SAR without vaccination.FindingsA total of 196 case-households and 55 control-households were recruited. Household SAR for rotavirus infection was high (65%); SAR for clinical disease was much lower (5%). Asymptomatic infection in control households was common (28%). Increasing disease severity was associated with increased risk of transmission of both rotavirus infection and disease to household contacts. Estimated VET was 39% (95% confidence interval 16-57%).InterpretationRotavirus vaccine has the potential to substantially reduce household rotavirus transmission. This should be considered in clinical and health economic assessments of vaccine impact.FundingWellcome Trust and NIH/NIAID.

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