Humoral Immune Responses following COVID-19 Vaccinations among Adults in Tanzania

Muhammad Bakari, Said Aboud, Mabula Kasubi, Bruno P. Mmbando, Nyanda Elias Ntinginya, Aifello Sichalwe, Omary S. Ubuguyu, Alex Magesa, Nancy Ladislaus Rutananukwa, Helmut Nyawale, Abisai Kisinda, Medard Beyanga, Pius G. Horumpende, Paulo S. Mhame, Liggle M. Vumilia, Lucy S. Mziray, Reuben Mkala, Elichilia Shao, Abel Makubi, Stephen E. Mshana, Rogath Kishimba

COVID-19 vaccination remains to be the most important intervention in the fight against the pandemic. The immunity among the vaccinated population and its durability can significantly vary due to various factors. This study investigated the humoral immune responses among individuals who received any of the COVID-19 vaccines approved for use in Tanzania. A total of 1048 randomly selected adults who received COVID-19 vaccines at different time points were enrolled and humoral immune responses (IR) were tested at baseline and three months later (960, 91.6%). The level of SARS-CoV-2 anti-spike/receptor binding domain (RBD) IgG, anti-nucleocapsid IgG, and IgM antibodies were determined using a commercially available chemiluminescent microparticle immunoassay. Descriptive data analysis was performed using STATA version 18 and R. At baseline, serum IgG against anti-spike/RBD was detected in 1010/1048 (96.4%) participants (95%CI: 94.9–97.5) and 98.3% (95%CI: 97.3–99) three months later. The IgG against the SARS-CoV-2 nucleocapsid proteins were detected in 40.8% and 45.3% of participants at baseline and follow-up, respectively. The proportion of seroconverters following vaccination and mean titers of anti-spike/RBD antibodies were significantly more among those who had past SARS-CoV-2 infection than in those with no evidence of past infection, (p < 0.001). Only 0.5% of those who had detectable anti-spike/RBD antibodies at baseline were negative after three months of follow-up and 1.5% had breakthrough infections. The majority of participants (99.5%) had detectable anti-spike/RBD antibodies beyond 6 months post-vaccination. The proportion of Tanzanians who mounted humoral IR following COVID-19 vaccination was very high. Seroconversions, as well as the mean titers and durability of humoral IR, were significantly enhanced by exposure to natural SARS-CoV-2 infection. In view of the limited availability of COVID-19 vaccines as well as challenges to completing subsequent doses, booster doses could only be suggested to high-risk groups.

Published at: 2023-12-23

Country wide surveillance reveals prevalent artemisinin partial resistance mutations with evidence for multiple origins and expansion of high level sulfadoxine-pyrimethamine resistance mutations in northwest Tanzania

Jonathan J. Juliano, David J. Giesbrecht, Alfred Simkin, Abebe A. Fola, Beatus M. Lyimo, Dativa Pereus, Catherine Bakari, Rashid A. Madebe, Misago D. Seth, Celine I. Mandara, Zachary R. Popkin-Hall, Ramadhan Moshi, Ruth B. Mbwambo, Karamoko Niaré, Bronwyn MacInnis, Filbert Francis, Daniel Mbwambo, Issa Garimo, Frank Chacky, Sijenunu Aaron, Abdallah Lusasi, Fabrizio Molteni, Ritha J. A. Njau, Samwel Lazaro, Ally Mohamed, Jeffrey A. Bailey, Deus S. Ishengoma

Emergence of artemisinin partial resistance (ART-R) in Plasmodium falciparum is a growing threat to the efficacy of artemisinin combination therapies (ACT) and the efforts for malaria elimination. The emergence of Plasmodium falciparum Kelch13 (K13) R561H in Rwanda raised concern about the impact in neighboring Tanzania. In addition, regional concern over resistance affecting sulfadoxine-pyrimethamine (SP), which is used for chemoprevention strategies, is high.

Published at: 2023-11-30

Malaria Species Positivity Rates Among Symptomatic Individuals Across Regions of Differing Transmission Intensities in Mainland Tanzania

Zachary R Popkin-Hall, Misago D Seth, Rashid A Madebe, Rule Budodo, Catherine Bakari, Filbert Francis, Dativa Pereus, David J Giesbrecht, Celine I Mandara, Daniel Mbwambo, Sijenunu Aaron, Abdallah Lusasi, Samwel Lazaro, Jeffrey A Bailey, Jonathan J Juliano, Deus S Ishengoma

Recent data indicate that non-Plasmodium falciparum species may be more prevalent than thought in sub-Saharan Africa. Although Plasmodium malariae, Plasmodium ovale spp., and Plasmodium vivax are less severe than P. falciparum, treatment and control are more challenging, and their geographic distributions are not well characterized.

Published at: 2023-11-22

Plasmodium falciparum pfhrp2 and pfhrp3 Gene Deletions Among Patients Enrolled at 100 Health Facilities Throughout Tanzania: February to July 2021

Eric Rogier, Nastassia Battle, Catherine Bakari, Misago D. Seth, Douglas Nace, Camelia Herman, Rashid A. Madebe, Celine I. Mandara, Beatus M. Lyimo, David J. Giesbrecht, Zachary R. Popkin-Hall, Filbert Francis, Daniel Mbwambo, Issa Garimo, Sijenunu Aaron, Abdallah Lusasi, Fabrizio Molteni, Ritha Njau, Jane A. Cunningham, Samwel Lazaro, Ally Mohamed, Jonathan J. Juliano, Jeffrey A. Bailey, Venkatachalam Udhayakumar, Deus S. Ishengoma

Plasmodium falciparum with the histidine rich protein 2 gene (pfhrp2) deleted from its genome can escape diagnosis by HRP2-based rapid diagnostic tests (HRP2-RDTs). The World Health Organization (WHO) recommends switching to a non-HRP2 RDT for P. falciparum clinical case diagnosis when pfhrp2 deletion prevalence causes ≥ 5% of RDTs to return false negative results. Tanzania is a country of heterogenous P. falciparum transmission, with some regions approaching elimination and others at varying levels of control. In concordance with the current recommended WHO pfhrp2 deletion surveillance strategy, 100 health facilities encompassing 10 regions of Tanzania enrolled malaria-suspected patients between February and July 2021. Of 7,863 persons of all ages enrolled and providing RDT result and blood sample, 3,777 (48.0%) were positive by the national RDT testing for Plasmodium lactate dehydrogenase (pLDH) and/or HRP2. A second RDT testing specifically for the P. falciparum LDH (Pf-pLDH) antigen found 95 persons (2.5% of all RDT positives) were positive, though negative by the national RDT for HRP2, and were selected for pfhrp2 and pfhrp3 (pfhrp2/3) genotyping. Multiplex antigen detection by laboratory bead assay found 135/7,847 (1.7%) of all blood samples positive for Plasmodium antigens but very low or no HRP2, and these were selected for genotyping as well. Of the samples selected for genotyping based on RDT or laboratory multiplex result, 158 were P. falciparum DNA positive, and 140 had sufficient DNA to be genotyped for pfhrp2/3. Most of these (125/140) were found to be pfhrp2+/pfhrp3+, with smaller numbers deleted for only pfhrp2 (n=9) or only pfhrp3 (n=6). No dual pfhrp2/3 deleted parasites were observed. This survey estimated that 0.24% (95% confidence interval: 0.08% to 0.39%) of false-negative HRP2-RDTs for symptomatic persons were due to pfhrp2 deletions in this 2021 Tanzania survey. These data provide evidence for HRP2-based diagnostics as currently accurate for P. falciparum diagnosis in Tanzania.

Published at: 2023-08-05

Implementation research of a cluster randomized trial evaluating the implementation and effectiveness of intermittent preventive treatment for malaria using dihydroartemisinin-piperaquine on reducing malaria burden in school-aged children in Tanzania: methodology, challenges, and mitigation

Geofrey Makenga, Misago D. Seth, Vito Baraka, Bruno P. Mmbando, Daniel P. Challe, Filbert Francis, Athanas Mhina, Daniel T. R. Minja, Mercy Chiduo, Celine Mandara, Edwin Liheluka, Samwel Gesase, Method Segeja, George Mtove, Mathias Kamugisha, Abdallah Lusasi, Frank Chacky, Anna David, Sumaiyya Thawer, Ally Mohamed, Samwel Lazaro, Fabrizio Molteni, Alex Nkayamba, Jean-Pierre Van geertruyden & John P. A. Lusingu

It has been more than 20 years since the malaria epidemiologic shift to school-aged children was noted. In the meantime, school-aged children (5–15 years) have become increasingly more vulnerable with asymptomatic malaria prevalence reaching up to 70%, making them reservoirs for subsequent transmission of malaria in the endemic communities. Intermittent Preventive Treatment of malaria in schoolchildren (IPTsc) has proven to be an effective tool to shrink this reservoir. As of 3rd June 2022, the World Health Organization recommends IPTsc in moderate and high endemic areas. Even so, for decision-makers, the adoption of scientific research recommendations has been stifled by real-world implementation challenges. This study presents methodology, challenges faced, and mitigations used in the evaluation of the implementation of IPTsc using dihydroartemisinin-piperaquine (DP) in three councils (Handeni District Council (DC), Handeni Town Council (TC) and Kilindi DC) of Tanga Region, Tanzania so as to understand the operational feasibility and effectiveness of IPTsc on malaria parasitaemia and clinical malaria incidence.

Published at: 2023-01-06

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