Immunogenicity and safety of two monovalent rotavirus vaccines, ROTAVAC® and ROTAVAC 5D® in Zambian infants.

BACKGROUND AND AIMS: ROTAVAC® (frozen formulation stored at -20 °C) and ROTAVAC 5D® (liquid formulation stable at 2-8 °C) are rotavirus vaccines derived from the 116E human neonatal rotavirus strain, developed and licensed in India. This study evaluated and compared the safety and immunogenicity of these vaccines in an infant population in Zambia. METHODS: We conducted a phase 2b, open-label, randomized, controlled trial wherein 450 infants 6 to 8 weeks of age were randomized equally to receive three doses of ROTAVAC or ROTAVAC 5D, or two doses of ROTARIX®. Study vaccines were administered concomitantly with routine immunizations. Blood samples were collected pre-vaccination and 28 days after the last dose. Serum anti-rotavirus IgA antibodies were measured by ELISA, with WC3 and 89-12 rotavirus strains as viral lysates in the assays. The primary analysis was to assess non-inferiority of ROTAVAC 5D to ROTAVAC in terms of the geometric mean concentration (GMC) of serum IgA (WC3) antibodies. Seroresponse and seropositivity were also determined. Safety was evaluated as occurrence of immediate, solicited, unsolicited, and serious adverse events after each dose. RESULTS: The study evaluated 388 infants in the per-protocol population. All three vaccines were well tolerated and immunogenic. The post-vaccination GMCs were 14.0 U/mL (95% CI: 10.4, 18.8) and 18.1 U/mL (95% CI: 13.7, 24.0) for the ROTAVAC and ROTAVAC 5D groups, respectively, yielding a ratio of 1.3 (95% CI: 0.9, 1.9), thus meeting the pre-set non-inferiority criteria. Solicited and unsolicited adverse events were similar across all study arms. No death or intussusception case was reported during study period. CONCLUSIONS: Among Zambian infants, both ROTAVAC and ROTAVAC 5D were well tolerated and the immunogenicity of ROTAVAC 5D was non-inferior to that of ROTAVAC. These results are consistent with those observed in licensure trials in India and support use of these vaccines across wider geographical areas.

Rural Malawians' perceptions of HIV risk behaviors and their sociocultural context.

Prevention remains key in the fight against HIV/AIDS. However, prevention requires understanding the sociocultural and economic context in which HIV-risk behaviors occur. This qualitative, descriptive study was part of the initial phase of a larger project to adapt and test a community-based HIV-prevention intervention. We conducted individual interviews with rural Malawian community leaders and focus groups with adult community residents to elicit perceptions of both sexual and non-sexual HIV-risk behaviors and their sociocultural context. Interviews and focus groups were conducted in Chichewa, audio-taped, transcribed and translated into English by bilingual co-investigators. Content analysis of transcripts was done collaboratively by US-based and Malawian co-investigators to confirm culturally accurate interpretation of data. Participants identified sexual and non-sexual HIV-risk behaviors and contextual factors that influence these behaviors, including gender relations, cultural practices, economic conditions and religion. Community leaders and residents voiced similar perspectives on risk behaviors, except that community leaders were much less likely than residents to discuss sexual transmission through participation in traditional cultural practices. We incorporated these study results in adapting our HIV-prevention intervention to the sociocultural context of rural Malawi. Study participation enhanced the community leader's and resident's interest in the intervention phase of the project.