Immune response to co-administration of measles, mumps, and rubella (MMR), and yellow fever vaccines: a randomized non-inferiority trial among one-year-old children in Argentina

BACKGROUND

In yellow fever (YF) endemic areas, measles, mumps, and rubella (MMR), and YF vaccines are often co-administered in childhood vaccination schedules. Because these are live vaccines, we assessed potential immune interference that could result from co-administration.

METHODS

We conducted an open-label, randomized non-inferiority trial among healthy 1-year-olds in Misiones Province, Argentina. Children were randomized to one of three groups (1:1:1): Co-administration of MMR and YF vaccines (MMR₁YF₁), MMR followed by YF vaccine four weeks later (MMR₁YF₂), or YF followed by MMR vaccine four weeks later (YF₁MMR₂). Blood samples obtained pre-vaccination and 28 days post-vaccination were tested for immunoglobulin G antibodies against measles, mumps, and rubella, and for YF virus-specific neutralizing antibodies. Non-inferiority in seroconversion was assessed using a -5% non-inferiority margin. Antibody concentrations were compared with Kruskal-Wallis tests.

RESULTS

Of 851 randomized children, 738 were correctly vaccinated, had ≥ 1 follow-up sample, and were included in the intention-to-treat population. Non-inferior seroconversion was observed for all antigens (measles seroconversion: 97.9% in the MMR₁YF₁ group versus 96.3% in the MMR₁YF₂ group, a difference of 1.6% [90% CI -1.5, 4.7]; rubella: 97.9% MMR₁YF₁ versus 94.7% MMR₁YF₂, a difference of 3.3% [-0.1, 6.7]; mumps: 96.7% MMR₁YF₁ versus 97.9% MMR₁YF₂, a difference of -1.3% [-4.1, 1.5]; and YF: 96.3% MMR₁YF₁ versus 97.5% YF₁MMR₂, a difference of -1.2% [-4.2, 1.7]). Rubella antibody concentrations and YF titers were significantly lower following co-administration; measles and mumps concentrations were not impacted.

CONCLUSION

Effective seroconversion was achieved and was not impacted by the co-administration, although antibody levels for two antigens were lower. The impact of lower antibody levels needs to be weighed against missed opportunities for vaccination to determine optimal timing for MMR and YF vaccine administration.

TRIAL REGISTRATION

The study was retrospectively registered in ClinicalTrials.gov (NCT03368495) on 11/12/2017.

Safety and immunogenicity of heterologous COVID-19 vaccine regimens to deal with product shortage: A randomised clinical trial in an elderly population

Objectives

In a context of COVID-19 vaccine shortages, this study sought to evaluate the safety and efficacy of receiving one dose of Gam-COVID-Vac rAd26 followed by a second COVID-19 vaccine dose of either Gam-COVID-Vac rAd5, ChAdOx1 nCoV-19 or BBIBP-CorV in a cohort of older adults.

Study design

Single-centre, randomised, open label, non-inferiority trial.

Methods

Adults aged ≥65 years who had received one dose of Gam-COVID-Vac rAd26 were randomised in a 1:1:1 ratio to receive a second-dose COVID-19 vaccination of either Gam-COVID-Vac rAd5, ChAdOx1 nCoV-19 or BBIBP-CorV. The primary outcome was the assessment of the humoral immune response to vaccination (i.e. antibody titres of SARS-CoV-2 spike protein at 28 days after second-dose vaccination). In addition, neutralising antibody titres at day 28 for the three schedules were measured.

Results

Of 85 participants who were enrolled in the study between 26 and July 30, 2021, 31 individuals were randomised to receive Gam-COVID-Vac rAd5, 27 to ChAdOx1 nCoV-19 and 27 to BBIBP-CorV. The mean age of participants was 68.2 years (SD 2.9) and 49 (57.6%) were female. Participants who received Gam-COVID-Vac rAd5 and ChAdOx1 nCoV1-19 showed significantly increased anti-S titres at 28 days after second-dose vaccination, but this magnitude of difference was not observed for those who received BBIBP-CorV. The ratio between the geometric mean at day 28 and baseline within each group was 11.8 (6.98-19.89) among patients assigned to Gam-COVID-Vac rAd26/rAd5, 4.81 (2.14-10.81) for the rAd26/ChAdOx1 nCoV-19 group and 1.53 (0.74-3.20) for the rAd26/BBIBP-CorV group. All of the schedules were shown to be safe.

Conclusions

The findings in this study contribute to the scarce information published on the safety and immunogenicity of Gam-COVID-Vac heterologous regimens and will help the development of guidelines and vaccine programme management.

Persistence of immunity and seroprotection 4 years after a primary vaccination schedule with a Hansenula polymorpha recombinant hepatitis B vaccine

To evaluate the persistence of the immune response in a population of healthy volunteers that had been vaccinated with a new Hansenula polymorpha recombinant hepatitis B vaccine in a previous clinical study 4 years before, we measured the titre of anti-HBs. All, but one of the evaluated volunteers remained protected. None of them had experienced any adverse event related to the vaccine from the moment of immunization, to the present. The vaccine proved to be immunogenic and to confer long-term protection in this group.