Group B streptococcus vaccination in pregnant women with or without HIV in Africa: A non-randomised phase 2, open-label, multicentre trial

Background: Neonates born to women infected with HIV are at increased risk for invasive group B streptococcus (GBS) disease. We aimed to compare safety and immunogenicity of trivalent glycoconjugate GBS vaccine in pregnant women with and without HIV in Malawi and South Africa. Methods: In our non-randomised phase 2, open-label, multicentre study, we recruited pregnant women attending two antenatal clinics, one in Blantyre, Malawi, and one in Soweto, Johannesburg, South Africa. Participants were divided into three groups on the basis of their HIV infection status (no infection, infection and high CD4 cell count [>350 cells per μL], and infection and low CD4 cell count [>50 to ≤350 cells per μL]) and received a 5 μg dose of glycoconjugate GBS vaccine (serotypes Ia, Ib, and III, with CRM197 [Novartis Vaccines, Siena, Italy]) intramuscularly at 24-35 weeks’ gestation. GBS serotype-specific antibody concentrations were measured before vaccination (day 1), day 15, day 31, and at delivery, and in infants at birth and day 42 of life. The primary outcomes were safety in mothers and infants and the amount of placental transfer of GBS serotype-specific antibodies from mothers to their infants. All immunogenicity and safety analyses were done on the full analysis set, including participants who, or whose mother, correctly received the vaccine and who provided at least one valid assessable serum sample. This study is registered with ClinicalTrials.gov, number NCT01412801. Findings: 270 women and 266 infants were enrolled between Sept 26, 2011, and Dec 4, 2012 (90 women and 87 infants without HIV, 89 and 88 with HIV and high CD4 cell counts, and 91 and 91 with HIV and low CD4 cell counts, respectively). Seven women were lost to follow-up, six withdrew consent, one died, and two relocated. Eight infants died or were stillborn and two were lost to follow-up. Across serotypes, fold change in antibody concentrations were higher for the HIV-uninfected group than the HIV-infected groups. Transfer ratios were similar across all three groups (0·49-0·72; transfer ratio is infant geometric mean antibody concentration in blood collected within 72 h of birth divided by maternal geometric mean antibody concentration in blood collected at delivery); however, at birth, maternally derived serotype-specific antibody concentrations were lower for infants born to women infected with HIV (0·52-1·62 μg/mL) than for those born to women not infected with HIV (2·67-3·91 μg/mL). 151 (57%) of 265 women reported at least one solicited adverse reaction: 39 (45%) of 87 women with HIV and low CD4 cell counts, 52 (59%) of 88 women with HIV and high CD4 cell counts, and 60 (67%) of 90 women in the HIV-uninfected group. 49 (18%) of 269 women had at least one adverse event deemed possibly related to the vaccine (six [7%] in the HIV and low CD4 cell count group, 12 [13%] in the HIV and high CD4 cell count group, and 21 [23%] in the HIV-uninfected group), as did three (1%) of 266 neonates (zero, two [1%], and one [1%]); none of these events was regarded as serious. Interpretation: The vaccine was less immunogenic in women infected with HIV than it was in those not infected, irrespective of CD4 cell count, resulting in lower levels of serotype-specific maternal antibody transferred to infants, which could reduce vaccine protection against invasive GBS disease. A validated assay and correlate of protection is needed to understand the potential protective value of this vaccine. Funding: Novartis Vaccines and Diagnostics division (now part of the GlaxoSmithKline group of companies), Wellcome Trust UK, Medical Research Council: Respiratory and Meningeal Pathogens Research Unit.

This non-randomised phase 2, open-label, multicentre study was done in two antenatal clinics, one in Blantyre, Malawi, and one in Soweto, Johannesburg, South Africa, between September, 2011, and December, 2012. Pregnant women were enrolled sequentially by study nurses into three groups in a 1:1:1 ratio on the basis of their HIV infection status and CD4 cell count until each of the groups was filled; the groups were HIV uninfected, HIV infected with a high CD4 cell count (>350 cells per μL), and HIV infected with a low CD4 cell count (>50 to ≤350 cells per μL). The study was done in accordance with the Declaration of Helsinki and the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use Guidelines for Good Clinical Practice. Written informed consent was obtained from women before enrolment. The protocol was approved by the National Health Sciences Research Committee (Malawi) and the University of Witwatersrand, Human Research Ethics Committee (South Africa). Use of an investigational GBS vaccine was approved by the Pharmacy, Medicines & Poisons Board, Malawi, and the Medicine Control Council, South Africa. Pregnant women aged 18–40 years between 24 and 35 weeks’ gestation were eligible. All women attending the clinics at the study sites were informed of the study. Those who fulfilled the study eligibility criteria and agreed to take part were enrolled after giving informed written consent. Women infected with HIV were eligible if their CD4 cell count was more than 50 cells per μL and they had WHO stage I or II disease. Exclusion criteria included receipt of a vaccine 15 days before enrolment (except tetanus toxoid and non-alum adjuvanted influenza vaccines); severe allergic reaction or hypersensitivity to previous vaccinations or vaccine component; fever at enrolment or acute infection up to 7 days before enrolment; any disorder associated with prolonged bleeding; immunosuppressive treatment within 30 days before enrolment; receipt of blood or blood products in the 12 weeks before enrolment; behavioural or cognitive impairment; and progressive or severe neurological disorder, seizure disorder, epilepsy, or Guillain-Barré syndrome. Twin pregnancies were included in the study (appendix). Carriage of GBS was not assessed or deemed an exclusion criterion for this study. Treatment of mothers and their babies, including HIV management, was provided by government services according to national guidelines, free at the point of care. Gestational age was estimated by (in order of preference) ultrasonography before 24 weeks’ gestation, date of last menstrual period, fundal height at 20–35 weeks’ gestation, or ultrasonography at 25–27 weeks’ gestation. CD4 cell counts were assessed using BD FACSCount (BD Biosciences, San Jose, CA, USA) and viral load was measured in Malawi using the Abbott RealTime HIV-1 assay (Abbott Laboratories, Abbott Park, IL, USA), and in South Africa using the Taqman version 2 HIV-1 assay (Roche, Pleasanton, CA, USA). Women were immunised with a 0·5 mL dose of non-adjuvanted CRM197-conjugated GBS vaccine (Novartis Vaccines, Siena, Italy) containing 5 μg of each capsular polysaccharide of serotypes Ia, Ib, and III, reconstituted in 0·9% sodium chloride. The vaccine was given intramuscularly into the non-dominant arm at 24–35 weeks’ gestation. For immunogenicity analysis, blood was collected from women before vaccination on day 1, at days 15 and 31 post-vaccination, and at delivery. For women infected with HIV, HIV-1 viral load and CD4 cell counts were measured before vaccination and the day of delivery. Cord blood or peripheral blood was collected from infants at birth and day 42. GBS serotype-specific antibody concentrations in women and infants were estimated using a previously described ELISA protocol at GlaxoSmithKline Clinical Sciences Laboratory, Marburg, Germany.18 In brief, antibody concentrations were assessed using 96-well plates, which were coated in 1 μg/mL human serum albumin-conjugated GBS polysaccharide representing the three vaccine serotypes. Serially diluted serum samples were incubated on the coated plates for 1 h at 37°C and an alkaline-phosphatase-conjugated goat anti-human IgG secondary antibody was added after washing and incubated for a further 90 min. After further washing, SeramunGelb pNPP was added to the plates and incubated for 30 min at room temperature, then the reaction was stopped with SeramunGelb stop. Antibody concentrations were calculated using Mikrowin 2000 software from optical density values measured at 405 nm using a BEP III ELISA processor. Because of lab constraints, serotype Ia ELISA testing was done in three batches, whereas all the testing for serotype Ib and III was done in one batch. Antibody concentrations were expressed as geometric mean concentrations (GMCs) with 95% CIs, calculated with the Clopper-Pearson method. Subgroup analysis was done for women on the basis of baseline serotype-specific antibody titres. The primary objective of this study was to compare the amount of placental transfer of GBS serotype-specific antibodies to the infants of pregnant women infected with HIV and those not infected after administration of investigational GBS vaccine. As a secondary objective, the concentrations of maternal serotype-specific GBS antibodies were assessed post-vaccination. An exploratory objective was the assessment of the kinetics of maternally derived antibodies in infants born to vaccinated women. Safety objectives were the assessment of solicited adverse reactions, unsolicited adverse events, serious adverse events, and obstetric outcomes. After immunisation, the women were observed for 30 min for any immediate adverse reactions. Adverse events and serious adverse events were graded on severity and possible relation to study vaccine by the investigator. A standardised approach was used to identify adverse events, which were defined as any untoward medical occurrence in a mother given the investigational vaccine or her infant that did not necessarily have a causal relation with this treatment. Solicited adverse reactions were recorded for 7 days post-vaccination with diary cards. Adverse events were collected up to day 31 post-vaccination, and adverse events requiring a physician’s visit, serious adverse events, and deaths were recorded for women and infants throughout the study. As part of the safety analysis the outcome of the pregnancy was assessed, including the health status of neonates (including Apgar score). Admission to hospital for a normal delivery was not deemed a serious adverse event in the context of this study. The sample sizes were calculated on the conservative assumption that only 60 participants per group would be enrolled, that there would be a 15% dropout rate, and that 80% of women would deliver infants that are at 37 weeks or more of gestation or weighed 2500 g or more at birth. Thus, a sample size of 40 per group would give about 95% power to detect an 8% difference in the percentage of placental transfer between any two study groups. However, if the maximum number of participants per group (90) were to be reached, under the same assumptions for the dropout rate and for the percentage of babies born at 37 weeks or more of gestation or weighing 2500 g or more at birth, the number of assessable participants would increase up to 60 per group, giving about 95% power to detect a 6·5% difference in the percentage of placental transfer between any two study groups. After determination of the sample size for the trial with and without babies born at less than 37 weeks’ gestation or less than 2500 g, we decided that both of these early gestation or underweight groups should be retained within the analysis. All serum analyses were done on the full analysis set, which included all mothers who correctly received the vaccine and who provided at least one valid assessable serum sample, and their neonates. Safety data were analysed descriptively for the safety set, which included all mothers who correctly received the study vaccination and who provided safety data, and their neonates. The primary objective was analysed using an ANCOVA model on log10-transformed maternal and infant GBS antibody levels, with HIV group and country as qualitative factors, and gestational age at delivery and birthweight as covariates. Multiplicity of testing across the three participant groups was adjusted for by using a significance level of 0·016 (ie, p=0·05/3). The null hypothesis was rejected if a significant difference was seen for all three serotypes. The secondary objective was analysed using an ANCOVA on log10-transformed maternal antibody concentrations at each relevant timepoint, with HIV group and country as qualitative factors, and baseline log10-antibody concentration as a covariate. Infant antibody concentrations at each timepoint were analysed using an ANOVA model, with maternal HIV group and country as qualitative factors and a significance level of 0·05. For analysis, any antibody concentrations that were below the lower limit of quantification (<LLQ) were set as half the LLQ (LLQ serotype Ia: 0·326 μg/mL, serotype Ib: 0·083 μg/mL, serotype III: 0·080 μg/mL). All statistical analyses were done with SAS version 9.1. This study is registered with ClinicalTrials.gov, number {"type":"clinical-trial","attrs":{"text":"NCT01412801","term_id":"NCT01412801"}}NCT01412801. The study sponsor was involved in all stages of the study, including manuscript development. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication. All authors agreed to submit the manuscript for publication. No honorarium, grant, or other form of payment was provided to authors, with the exception of funding needed to do the study.

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