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Despite the contribution of currently licensed live, oral rotavirus vaccines (LORVs) to alleviating the burden of severe disease and death from rotavirus gastroenteritis, those vaccines have proven less efficacious in resource-limited settings than in high- and middle-income countries. It has been proposed that the residual burden of rotavirus disease might be overcome with parenterally administered vaccines, or next-generation rotavirus vaccines (NGRV). To better define the progress of development of these vaccines, a meeting of vaccine developers and manufacturers engaged in NGRV research and development was convened in Geneva in June 2019. Several NRGVs are in various stages of preclinical development, and two have already entered clinical testing. The vaccine platforms include subunit protein, inactivated whole virus, virus-like particle and RNA-based vaccines. Meeting participants included groups involved in NGRV development, scientists investigating correlates of protection of rotavirus vaccines, and representatives of international organizations with insight into considerations for vaccine introduction. This report summarizes the presentations shared at the meeting.

Efficacy of live oral rotavirus vaccines is reduced in low-income compared with high-income settings. Parenteral non-replicating rotavirus vaccines might offer benefits over oral vaccines. We assessed the safety and immunogenicity of the P2-VP8-P[8] subunit rotavirus vaccine at different doses in South African toddlers and infants. This double-blind, randomised, placebo-controlled, dose-escalation trial was done at a single research unit based at a hospital in South Africa in healthy HIV-uninfected toddlers (aged 2 to <3 years) and term infants (aged 6 to <8 weeks, without previous rotavirus vaccination). Block randomisation (computer-generated, electronic allocation) was used to assign eligible toddlers (in a 6:1 ratio) and infants (in a 3:1 ratio) in each dose cohort (10 μg, followed by 30 μg, then 60 μg if doses tolerated) to parenteral P2-VP8-P[8] subunit rotavirus or placebo injection. The two highest tolerated doses were then assessed in an expanded cohort (in a 1:1:1 ratio). Parents of participants and clinical, data, and laboratory staff were masked to treatment assignment. P2-VP8-P[8] vaccine versus placebo was assessed first in toddlers (single injection) and then in infants (three injections 4 weeks apart). The primary safety endpoints were local and systemic reactions within 7 days after each injection, adverse events within 28 days after each injection, and all serious adverse events, assessed in toddlers and infants who received at least one dose. In infants receiving all study injections, primary immunogenicity endpoints were anti-P2-VP8-P[8] IgA and IgG and neutralising antibody seroresponses and geometric mean titres 4 weeks after the third injection. This trial is registered at ClinicalTrials.gov, number NCT02109484. Between March 17, 2014, and Sept 29, 2014, 42 toddlers (36 to vaccine and six to placebo) and 48 infants (36 to vaccine and 12 to placebo) were enrolled in the dose-escalation phase, in which the 30 μg and 60 μg doses where found to be the highest tolerated doses. A further 114 infants were enrolled in the expanded cohort between Nov 3, 2014, and March 20, 2015, and all 162 infants (12 assigned to 10 μg, 50 to 30 μg, 50 to 60 μg, and 50 to placebo) were included in the safety analysis. Serum IgA seroresponses were observed in 38 (81%, 95% CI 67–91) of 47 infants in the 30 μg group and 32 (68%, 53–81) of 47 in the 60 μg group, compared with nine (20%, 10–35) of 45 in the placebo group; adjusted IgG seroresponses were seen in 46 (98%, 89–100) of 47 infants in the 30 μg group and 47 (100%; 92–100) of 47 in the 60 μg group, compared with four (9%, 2·5–21) of 45 in the placebo group; and adjusted neutralising antibody seroresponses against the homologous Wa-strain were seen in 40 (85%, 72–94) of 47 infants in both the 30 μg and 60 μg groups, compared with three (7%, 1·4–18) of 45 participants in the placebo group. Solicited reactions following any injection occurred with similar frequency and severity in participants receiving vaccine and those receiving placebo. Unsolicited adverse events were mostly mild and occurred at a similar frequency between groups. Eight serious adverse events (one with placebo, two with 30 μg, and five with 60 μg) occurred in seven infants within 28 days of any study injection, none of which were deemed related to study treatment. The parenteral P2-VP8-P[8] vaccine was well tolerated and immunogenic in infants, providing a novel approach to vaccination against rotavirus disease. On the basis of these results, a phase 1/2 trial of a trivalent P2-VP8 (P[4], P[6], and P[8]) subunit vaccine is underway at three sites in South Africa. Bill & Melinda Gates Foundation.

There is no licensed vaccine against enterotoxigenic Escherichia coli (ETEC), a major cause of diarrhea-associated morbidity and mortality among infants and children in low-income countries and travelers. The results of this vaccination/challenge study demonstrate strong protection by an attenuated ETEC vaccine candidate, ACE527, when co-administered with a mucosal adjuvant, the double-mutant heat-labile toxin (dmLT) of ETEC. Sixty healthy adults participated in a randomized, placebo-controlled, double-blind study with three doses of lyophilized ACE527 (∼3 × 109 of each strain per dose) administered orally with or without dmLT adjuvant (25 µg/dose). Six months later, 36 of these volunteers and a control group of 21 unvaccinated volunteers were challenged with virulent ETEC strain H10407. The primary outcome was severe diarrhea, defined as passing >800 g of unformed stools during the inpatient period following challenge. The vaccine was well tolerated and induced robust immune responses to key antigens. The protective efficacy (PE) against the primary outcome of severe diarrhea was 65.9% (95% confidence interval [CI] 5.4–87.7, p = 0.003). Among subjects receiving the adjuvanted vaccine, the attack rate of severe diarrhea was 23.1, while in unimmunized controls it was 67.7%. The PE against diarrhea of any severity was 58.5% (95% CI 3.8– 82.1, p = 0.016). There was a strong inverse correlation between shedding of the vaccine strain after either of the first two doses and absence of severe diarrhea upon challenge (RR = 0.29, 95% CI 0.08–1.05, p = 0.041). Challenge strain shedding was 10-fold lower in those receiving the adjuvant than in those receiving vaccine alone. The unadjuvanted vaccine was not protective (PE = 23.1%). The results of this study support further development of ACE527 + dmLT as a vaccine for children in endemic countries and travelers. This is the first clinical demonstration that dmLT can contribute significantly to vaccine efficacy and may warrant testing with other oral vaccines. (ClinicalTrials.gov registration: NCT01739231).

•Pentavalent reassortant rotavirus vaccine was tested for efficacy in infants.•The vaccine (BRV-PV) showed excellent tolerability and a good safety profile.•Primary analysis efficacy was 36% against SRVGE and up to 60.5% against VSRVGE.•The efficacy through 2years of age was 39.5% (SRVGE) and 54.7% (VSRVGE).•The intent to treat analyses confirmed all the per protocol analyses. Rotavirus is the most common cause of moderate-to-severe infant diarrhoea in developing countries, resulting in enormous morbidity, mortality, and economic burden. A bovine-human reassortant pentavalent rotavirus vaccine (BRV-PV) targeting the globally most common strains was developed in India and tested in a randomized, double-blind, placebo-controlled end-point driven Phase III efficacy clinical trial implemented at six sites across India. Infants 6 to 8weeks of age were randomized (1:1) to receive three oral doses of BRV-PV or placebo at 6, 10, and 14weeks of age along with routine vaccines. Home visit surveillance was conducted to detect severe rotavirus gastroenteritis (SRVGE) and safety outcomes until the children reached two years of age. A total of 3749 infants received BRV-PV while 3751 received placebo. At the time of the primary end-point (when the minimum number of cases needed for analysis were accrued) the vaccine efficacy against SRVGE was 36% (95% CI 11.7, 53.6, p=0.0067) in the per protocol (PP) analysis, and 41.9% (95% CI 21.1, 57.3, p=0.0005) in the intent to treat (ITT) analysis. Vaccine efficacy over the entire follow-up period (until children reached two years of age) was 39.5% (95% CI 26.7, 50, p<0.0001) in the PP analysis and 38.8% (95% CI, 26.4, 49, p<0.0001) in the ITT analysis. Vaccine efficacy against the very severe rotavirus cases (VSRVGE, Vesikari score≥16) was 60.5% (95% CI 17.7, 81, p=0.0131) at the time of the primary analysis and 54.7% (95% CI 29.7, 70.8, p=0.0004) for the complete follow-period in the PP population. The incidence of solicited, unsolicited, and serious adverse events were similar in both the vaccine and placebo groups. Likewise, the number of intussusceptions and deaths were similar between both groups. Thus, BRV-PV is an effective, well tolerated and safe vaccine in Indian infants. (Trial registration: Clinical Trials.Gov [NCT 02133690] and Clinical Trial Registry of India [CTRI/2013/05/003667]).

The 2nd Next Generation Rotavirus Vaccine Developers Meeting, sponsored by PATH and the Bill and Melinda Gates Foundation, was held in London, UK (7–8 June 2022), and attended by vaccine developers and researchers to discuss advancements in the development of next-generation rotavirus vaccines and to consider issues surrounding vaccine acceptability, introduction, and uptake. Presentations included updates on rotavirus disease burden, the impact of currently licensed oral vaccines, various platforms and approaches for next generation rotavirus vaccines, strategies for combination pediatric vaccines, and the value proposition for novel parenteral rotavirus vaccines. This report summarizes the information shared at the convening and poses various topics worthy of further exploration.

A correlate of protection for rotavirus (RV) has not been consistently identified. Shedding of RV following an oral rotavirus vaccine (ORV) challenge has been investigated as a potential model to assess protection of parenteral RV vaccines. We previously showed that shedding of a challenge ORV dose was significantly reduced among recipients of a parenteral monovalent RV subunit vaccine (P2-VP8-P[8]) compared to placebo recipients. This secondary data analysis assessed the association between fecal shedding of RV, as determined by ELISA one week after receipt of a Rotarix challenge dose at 18 weeks of age, and serum RV-specific antibody responses, one and six months after vaccination with the third dose of the P2-VP8-P[8] vaccine or placebo. We did not find any association between serum RV-specific immune responses measured one month post-P2-VP8-P[8] vaccination and fecal shedding of RV post-challenge. At nine months of age, six months after the third P2-VP8-P[8] or placebo injection and having received three doses of Rotarix, infants shedding RV demonstrated higher immune responses than non-shedders, showing that RV shedding is reflective of vaccine response following ORV. Further evaluation is needed in a larger sample before fecal shedding of an ORV challenge can be used as a measure of field efficacy in RV vaccine trials.

While live oral rotavirus vaccines (LORVs) are effective at preventing severe rotavirus gastroenteritis (SRVGE), they perform sub-optimally in the settings with the highest burden. Parenteral rotavirus vaccines could have greater efficacy by bypassing the gut, where interference with LORVs may occur. A novel parenteral rotavirus subunit vaccine (TV P2-VP8) was evaluated in a Phase 3 study for safety, immunogenicity, and relative efficacy in healthy African infants. Participating infants were randomized at 6–8 weeks of age to receive either three doses of TV P2-VP8 intramuscularly (IM) plus oral placebo or two doses of ROTARIX® (oral) plus IM placebo. The trial was designed to enroll a total of 8200 participants in two stages separated by an interim analysis conducted upon accrual of a predetermined number of SRVGE cases. Data at interim analysis indicated a low probability of demonstrating TV P2-VP8 superiority compared to ROTARIX in prevention of SRVGE, and the study was closed early. 4055 infants were enrolled and provided safety data. TV P2-VP8 was safe and well tolerated, with no safety concerns indicated. Virus neutralizing and IgG binding antibody seroresponses to TV-P2-VP8 were detected in most participants. The crude attack rates of SRVGE in the per-protocol population (n = 3477) were 4.51 % (TV P2-VP8) and 2.57 % (ROTARIX). The relative vaccine efficacy (RVE) against SRVGE for TV P2-VP8 was −77.68 % (95 % CI, −162.38, −21.54). The RVE against SRVGE in the first and second year of life was −91.67 % (95 % CI, −199.20, −24.35) and − 31.97 % (95 % CI, −220.37, 44.49), respectively. The RVE against rotavirus gastroenteritis of any severity was −47.78 % (95 % CI, −89.63, −15.59). TV P2-VP8 provided inferior protection against SRVGE compared to ROTARIX. The vaccine candidate was safe, immunogenic, and well-tolerated by infants. Continued efforts are needed to identify alternative rotavirus vaccines with improved efficacy in LMICs. Trial Registration:NCT04010448; PACTR201907491834482. •The TV P2-VP8 vaccine candidate was safe and immunogenic.•Three doses of TV P2-VP8 were inferior to two doses of ROTARIX® in preventing severe rotavirus gastroenteritis.•Study provides insight to guide future development of rotavirus vaccine candidates.

•The killed oral ETEC vaccine ETVAX ± dmLT adjuvant was safe in Bangladeshi adults.•All vaccinees responded to all 5 primary vaccine antigens in ALS specimens.•A majority of vaccinees responded to ≥4 antigens in plasma specimens.•A sensitive electrochemiluminescence assay was established for small sample volumes.•ALS responses measured by electrochemiluminescence and ELISA assays correlated well. The safety and immunogenicity of the second generation oral enterotoxigenic Escherichia coli (ETEC) vaccine ETVAX, consisting of inactivated recombinant E. coli strains over-expressing the colonization factors (CFs) CFA/I, CS3, CS5 and CS6 and the heat labile toxoid LCTBA, were evaluated in Bangladeshi volunteers. To enable analysis of antibody responses against multiple vaccine antigens for subsequent use in small sample volumes from children, a sensitive electrochemiluminescence (ECL) assay for analysis of intestine-derived antibody-secreting cell responses using the antibodies in lymphocyte secretions (ALS) assay was established using Meso Scale Discovery technology. Three groups of Bangladeshi adults (n = 15 per group) received two oral doses of ETVAX with or without double mutant LT (dmLT) adjuvant or placebo in the initial part of a randomized, double-blind, placebo-controlled, age-descending, dose-escalation trial. CF- and LTB-specific ALS and plasma IgA responses were analyzed by ECL and/or ELISA. ETVAX was safe and well tolerated in the adults. Magnitudes of IgA ALS responses determined by ECL and ELISA correlated well (r = 0.85 to 0.98 for the five primary antigens, P < 0.001) and ECL was selected as the ALS readout method. ALS IgA responses against each of the primary antigens were detected in 87–100% of vaccinees after the first and in 100% after the second vaccine dose. Plasma IgA responses against different CFs and LTB were observed in 62–93% and 100% of vaccinees, respectively. No statistically significant adjuvant effect of dmLT on antibody responses to any antigen was detected, but the overall antigenic breadth of the plasma IgA response tended to favor the adjuvanted vaccine when responses to 4 or more or 5 vaccine antigens were considered. Responses in placebo recipients were infrequent and mainly detected against single antigens. The promising results in adults supported testing ETVAX in descending age groups of children. ClinicalTrials.gov Identifier: NCT02531802.

Reducing the risks of vaccine-derived polioviruses and vaccine-associated paralytic poliomyelitis motivated the development of novel types 1 and 3 oral poliovirus vaccines (nOPV1 and nOPV3, respectively), designed to have similar safety and immunogenicity and improved genetic stability (to reduce risk of reversion to neurovirulence) relative to types 1 or 3 Sabin-strain OPVs. We aimed to assess the safety and immunogenicity of nOPV1 and nOPV3 in healthy adults. We did a first-in-human, observer-masked, multicentre, phase 1 randomised controlled trial in healthy adults at four centres in the USA. Participants were block randomised, stratified by site and according to polio vaccination history (inactivated poliovirus vaccine [IPV] only [hereafter IPV participants] or regimens including OPV [hereafter OPV participants]), and randomly assigned to receive either nOPV or homotypic Sabin-strain monovalent OPV (mOPV). IPV participants received a single dose of nOPV1 or mOPV1 (cohort 1) or nOPV3 or mOPV3 (cohort 3) and OPV participants received two doses 28 days apart of nOPV1 or mOPV1 (cohort 2) or nOPV3 or mOPV3 (cohort 4). The primary outcome was safety among vaccinated participants. Secondary outcomes included homotypic serum neutralising antibody responses measured before and 28 days after each dose in a per-protocol population, and faecal viral shedding mainly in IPV participants assessed up to 56 days following each dose among vaccinated participants. This study was registered with ClinicalTrials.gov (NCT04529538) and is complete. Between May 6, 2021 and Feb 17, 2023, 377 individuals were assessed for eligibility, 226 were randomly assigned, and 205 receive at least one dose of nOPV1 (n=70), mOPV1 (n=45), nOPV3 (n=54), or mOPV3 (n=36). No serious adverse events were observed. Most adverse events were mild, severe events were rare, and solicited events were balanced across groups. Severe solicited events were predominantly fatigue, occurring in 1–4% of participants across all groups except for mOPV1 recipients in whom no such events were reported, and one case of nausea and vomiting in an mOPV1 recipient, and one case of abdominal pain in an nOPV1 recipient. Two (3%) participants in the nOPV1 groups (one reporting severe fatigue, headache, and myalgia, and one reporting abdominal pain) and one (2%) participant in the mOPV1 groups (kidney infection) reported a severe unsolicited adverse event within 28 days. Homotypic seroprotection was nearly 100% at baseline and was 100% 28 days after the first dose. Homotypic seroconversion rates after a single dose were high and similar for nOPV and mOPV (ranging from 86% to 100% for nOPV and from 86% to 93% for mOPV). Similar rates of viral shedding were observed among participants receiving nOPV or mOPV. Peak viral shedding rate detected via PCR among IPV participants was 100% on day 8 after a dose, across groups. nOPV1 and nOPV3 were well tolerated and showed similar immunogenicity and shedding profiles to mOPV1 and mOPV3, respectively, supporting progression of these vaccine candidates to phase 2 studies. Bill & Melinda Gates Foundation.

The P2-VP8 subunit vaccine for the prevention of rotavirus gastroenteritis is comprised of a truncated VP8 subunit protein from the rotavirus Wa strain (G1[P8]) fused to the tetanus toxin P2 epitope, and adsorbed on aluminum hydroxide for intramuscular administration. Three groups of 16 adults were randomized to receive three injections of P2-VP8 (12) or placebo (4) at doses of 10, 30 or 60μg of vaccine. IgG and IgA antibodies to P2-VP8 were assessed by ELISA in serum and lymphocyte supernatant (ALS). Serum samples were tested for neutralizing antibodies to homologous and heterologous strains of rotavirus. The vaccine was well-tolerated. All vaccine recipients demonstrated significant IgA responses and all but one demonstrated IgG responses; in the 60μg cohort, geometric mean titers (GMTs) rose 70- and 80-fold for IgA and IgG, respectively. Homologous neutralizing antibody responses were observed in about half of participants in all three dose cohorts; in the 60μg cohort, GMTs against Wa rose from 128 to 992. Neutralizing antibody responses were robust to P[8] strains, moderate to P[4] strains and negligible to P[6] strains. ALS IgA responses were dose dependent. The P2-VP8 subunit vaccine was well tolerated and evoked promising immune responses. NCT01764256