Title
Incidence of Plasmodium falciparum malaria infection in 6-month to 45-year-olds on selected areas of Bioko Island, Equatorial Guinea
Date Issued
01 December 2021
Access level
open access
Resource Type
journal article
Author(s)
Nchama V.U.N.N.
Said A.H.
Mtoro A.
Bidjimi G.O.
Owono M.A.
Maye E.R.M.
Mangue M.E.O.
Okomo G.N.N.
Pasialo B.E.N.
Ondo D.M.
Lopez M.S.A.
Mochomuemue F.L.
Obono M.O.
Besaha J.C.M.
Jongo S.A.
Kamaka K.
Kibondo U.A.
Athuman T.
Falla C.C.
Eyono J.N.M.
Smith J.M.
García G.A.
Raso J.
Nyakarungu E.
Mpina M.
Schindler T.
Daubenberger C.
Lemiale L.
Billingsley P.F.
Sim B.K.L.
Richie T.L.
Church L.W.P.
Olotu A.
Tanner M.
Hoffman S.L.
Abdulla S.
Medical Care Development International
Publisher(s)
BioMed Central Ltd
Abstract
Background: Extensive malaria control measures have been implemented on Bioko Island, Equatorial Guinea over the past 16 years, reducing parasite prevalence and malaria-related morbidity and mortality, but without achieving elimination. Malaria vaccines offer hope for reducing the burden to zero. Three phase 1/2 studies have been conducted successfully on Bioko Island to evaluate the safety and efficacy of whole Plasmodium falciparum (Pf) sporozoite (SPZ) malaria vaccines. A large, pivotal trial of the safety and efficacy of the radiation-attenuated Sanaria® PfSPZ Vaccine against P. falciparum is planned for 2022. This study assessed the incidence of malaria at the phase 3 study site and characterized the influence of socio-demographic factors on the burden of malaria to guide trial design. Methods: A cohort of 240 randomly selected individuals aged 6 months to 45 years from selected areas of North Bioko Province, Bioko Island, was followed for 24 weeks after clearance of parasitaemia. Assessment of clinical presentation consistent with malaria and thick blood smears were performed every 2 weeks. Incidence of first and multiple malaria infections per person-time of follow-up was estimated, compared between age groups, and examined for associated socio-demographic risk factors. Results: There were 58 malaria infection episodes observed during the follow up period, including 47 first and 11 repeat infections. The incidence of malaria was 0.25 [95% CI (0.19, 0.32)] and of first malaria was 0.23 [95% CI (0.17, 0.30)] per person per 24 weeks (0.22 in 6–59-month-olds, 0.26 in 5–17-year-olds, 0.20 in 18–45-year-olds). Incidence of first malaria with symptoms was 0.13 [95% CI (0.09, 0.19)] per person per 24 weeks (0.16 in 6–59-month-olds, 0.10 in 5–17-year-olds, 0.11 in 18–45-year-olds). Multivariate assessment showed that study area, gender, malaria positivity at screening, and household socioeconomic status independently predicted the observed incidence of malaria. Conclusion: Despite intensive malaria control efforts on Bioko Island, local transmission remains and is spread evenly throughout age groups. These incidence rates indicate moderate malaria transmission which may be sufficient to support future larger trials of PfSPZ Vaccine. The long-term goal is to conduct mass vaccination programmes to halt transmission and eliminate P. falciparum malaria.
Volume
20
Issue
1
Language
English
OCDE Knowledge area
Medicina tropical
Scopus EID
2-s2.0-85110804133
PubMed ID
Source
Malaria Journal
Sponsor(s)
The trial was funded by a public–private partnership, the Equatorial Guinea Malaria Vaccine Initiative, made up of the Government of Equatorial Guinea Ministries of Mines and Hydrocarbons, and Health and Social Welfare, Marathon Equatorial Guinea Production Limited, Noble Energy, Atlantic Methanol Production Company, and the Equatorial Guinea Liquefied Natural Gas Company. We would like to express our sincere gratitude to study participants and their parents for their participation in the study. We appreciate the contribution of other study staff including nurses, community mobilizers, and data entry and laboratory technicians who helped in the implementation and data collection process for the study. We also thank the staff of Equatorial Guinea, Ministry of Health and Social Welfare (EGMOHSW), Medical Care Development International (MCDI), Sanaria Inc. and Marathon Equatorial Guinea Production Limited, especially, His Excellency the Vice Minister of Health Mitoha Ondo?o Ayekaba, Mr. Wonder Phiri, Mr. Bonifacio Manguire Nlavo and Dr. Carl Maas who played an important role in the successful completion of the study.
Sources of information: Directorio de Producción Científica Scopus