Could less be more? Accounting for fractional-dose regimens and different number of vaccine doses when measuring the impact of the RTS, S/AS01E malaria vaccine

BACKGROUND

The RTS, S/AS01E malaria vaccine (RTS, S) is recommended for children in moderate-to-high Plasmodium falciparum malaria transmission areas. This phase 2b trial (NCT03276962) evaluates RTS, S fractional- and full-dose regimens in Ghana and Kenya.

METHODS

1500 children aged 5-17 months were randomised (1:1:1:1:1) to receive RTS, S or rabies control vaccine. RTS, S groups received two full RTS, S doses at month (M)0/M1 followed by either full (groups R012-20, R012-14-26) or fractional (1/5) doses (groups Fx012-14-26, Fx017-20-32).

RESULTS

At M32 post-first dose, vaccine efficacy (VE) against clinical malaria (all episodes) ranged from 38% (R012-20; 95%CI: 24-49) to 53% (R012-14-26; 95%CI: 42-62). Vaccine impact estimates (cumulative number of malaria cases averted/1000 children vaccinated) were 1344 (R012-20), 2450 (R012-14-26), 2273 (Fx012-14-26), 2112 (Fx017-20-32). To account for differences in vaccine volume (fractional- versus full-dose), in a post-hoc analysis, we also estimated cases averted/1000 RTS, S full-dose equivalents: 336 (R012-20), 490 (R012-14-26), 874 (Fx012-14-26), 880 (Fx017-20-32).

CONCLUSIONS

VE against clinical malaria was similar in all RTS, S groups. Vaccine impact accounting for full-dose equivalence suggests that using fractional-dose regimens could be a viable dose-sparing strategy. If borne out through trial end (M50), these observations underscore the means to reduce cost per regimen with a goal of maximising impact and optimising supply.

Assent, parental consent and reconsent for health research in Africa: thematic analysis of national guidelines and lessons from the SickleInAfrica registry

The enrolment of children and adolescents in health research requires that attention to be paid to specific assent and consent requirements such as the age range for seeking assent; conditions for parental consent (and waivers); the age group required to provide written assent; content of assent forms; if separate assent and parental consent forms should be used, consent from emancipated young adults; reconsent at the age of adulthood when a waiver of assent requirements may be appropriate and the conditions for waiving assent requirements. There is however very little available information for researchers and ethics committees on how to navigate these different issues. To provide guidance to research initiatives, the SickleInAfrica consortium conducted a thematic analysis of a sample of research ethics guidelines and procedures in African countries, to identify guidance for assent requirements in health research. The thematic analysis revealed that 12 of 24 African countries specified the age group for which assent is required. The minimum age for written assent varied across the countries. Five countries, Algeria, Botswana, Cameroon, Nigeria and The Democratic Republic of Congo require consent from both parents/family council in certain circumstances. Botswana, Nigeria, South Africa and Uganda have specific assent/consent requirements for research with emancipated minors. South Africa and Algeria requires re-consent at onset of adulthood. Five countries (Botswana, Cameroon, Nigeria, South Africa and Tanzania) specified conditions for waiving assent requirements. The CIOMS and the ICH-GCP guidelines had the most comprehensive information on assent requirements compared to other international guidelines. An interactive map with assent requirements for different African countries is provided. The results show a major gap in national regulations for the inclusion of minors in health research. The SickleInAfrica experience in setting up a multi-country SCD registry in Africa highlights the need for developing and harmonising national and international guidelines on assent and consent requirements for research involving minors. Harmonisation of assent requirements will help facilitate collaborative research across countries.

Bloodstream infection with Acinetobacter baumanii in a Plasmodium falciparum positive infant: a case report

Background

The increasing incidence of multi-antibiotic-resistant bacterial infections, coupled with the risk of co-infections in malaria-endemic regions, complicates accurate diagnosis and prolongs hospitalization, thereby increasing the total cost of illness. Further, there are challenges in making the correct choice of antibiotic treatment and duration, precipitated by a lack of access to microbial culture facilities in many hospitals in Ghana. The aim of this case report is to highlight the need for blood cultures or alternative rapid tests to be performed routinely in malaria patients, to diagnose co-infections with bacteria, especially when symptoms persist after antimalarial treatment.

Case presentation

A 6-month old black female child presented to the Agogo Presbyterian Hospital with fever, diarrhea, and a 3-day history of cough. A rapid diagnostic test for malaria and Malaria microscopy was positive for P. falciparum with a parasitemia of 224 parasites/μl. The patient was treated with Intravenous Artesunate, parental antibiotics (cefuroxime and gentamicin) and oral dispersible zinc tablets in addition to intravenous fluids. Blood culture yielded Acinetobacter baumanii, which was resistant to all of the third-generation antibiotics included in the susceptibility test conducted, but sensitive to ciprofloxacin and gentamicin. After augmenting treatment with intravenous ciprofloxacin, all symptoms resolved.

Conclusion

Even though this study cannot confirm whether the bacterial infection was nosocomial or otherwise, the case highlights the necessity to test malaria patients for possible co-infections, especially when fever persists after parasites have been cleared from the bloodstream. Bacterial blood cultures and antimicrobial susceptibility testing should be routinely performed to guide treatment options for febril illnesses in Ghana in order to reduce inappropriate use of broad-spectrum antibiotics and limit the development of antimicrobial resistance.

Central Nervous System Virus Infection in African Children with Cerebral Malaria

We aimed to identify the contribution of central nervous system (CNS) viral coinfection to illness in African children with retinopathy-negative or retinopathy-positive cerebral malaria (CM). We collected cerebrospinal fluid (CSF) from 272 children with retinopathy-negative or retinopathy-positive CM and selected CSF from 111 of these children (38 retinopathy positive, 71 retinopathy negative, 2 retinopathy unknown) for analysis by metagenomic next-generation sequencing. We found CSF viral coinfections in 7/38 (18.4%) retinopathy-positive children and in 18/71 (25.4%) retinopathy-negative children. Excluding HIV-1, human herpesviruses (HHV) represented 61% of viruses identified. Excluding HIV-1, CNS viral coinfection was equally likely in children who were retinopathy positive and retinopathy negative (P = 0.1431). Neither mortality nor neurological morbidity was associated with the presence of virus (odds ratio [OR] = 0.276, 95% CI: 0.056-1.363). Retinopathy-negative children with a higher temperature, lower white blood cell count, or being dehydrated were more likely to have viral coinfection. Level of consciousness at admission was not associated with CNS viral coinfection in retinopathy-negative children. Viral CNS coinfection is unlikely to contribute to coma in children with CM. The herpesviruses other than herpes simplex virus may represent incidental bystanders in CM, reactivating during acute malaria infection.

Pharmacokinetics of First-Line Antituberculosis Drugs Using WHO Revised Dosage in Children With Tuberculosis With and Without HIV Coinfection

BACKGROUND

Pharmacokinetic data on the first-line antituberculosis drugs using the World Health Organization (WHO) revised dosages for children are limited. We investigated the pharmacokinetics of these drugs in children who were mostly treated with revised dosages.

METHODS

Children with tuberculosis on first-line therapy for at least 4 weeks had blood samples collected at predose, 1, 2, 4, and 8 hours postdose. Drug concentrations were determined by validated liquid chromatography mass spectrometry methods, and pharmacokinetic parameters were calculated using noncompartmental analysis. Factors associated with plasma peak concentration (C_max) and the area under the time-concentration curve 0-8 hours (AUC_0-8h) of each drug was examined using univariate and multivariate analysis.

RESULTS

Of the 62 children, 32 (51.6%) were male, 29 (46.8%) were younger than 5 years old, and 28 (45.2%) had human immunodeficiency virus (HIV) coinfection. Three patients had undetectable pyrazinamide and ethambutol concentrations. The median (interquartile range) AUC_0-8h for isoniazid was 17.7 (10.2-23.4) µg·h mL^-1, rifampin was 26.0 (15.3-36.1) µg·h mL^-1, pyrazinamide was 144.6 (111.5-201.2) µg·h mL^-1, and ethambutol was 6.7 (3.8-10.4) µg·h mL^-1. Of the children who received recommended weight-band dosages, 44/51 (86.3%), 46/56 (82.1%), 27/56 (48.2%), and 21/51 (41.2%) achieved target C_max for isoniazid, pyrazinamide, ethambutol, and rifampin, respectively. In multivariate analysis, age, sex, HIV coinfection status, and drug dosage in milligrams per kilogram were associated with the drugs' plasma drug C_max or AUC_0-8h.

CONCLUSIONS

The revised dosages appeared to be adequate for isoniazid and pyrazinamide, but not for rifampin or ethambutol in this population. Higher dosages of rifampin and ethambutol than currently recommended may be required in most children.