The University of California (UC) San Diego in the US has joined a Phase II clinical trial to assess various Covid-19 booster vaccines. 

Named COVAIL, the trial is sponsored by the National Institutes of Health unit National Institute of Allergy and Infectious Diseases (NIAID).

It will analyse whether various regimens of Moderna-manufactured vaccines can boost immune responses in adults who have previously received the initial vaccine series and a first booster vaccine.

COVAIL is led by the Emory Vaccine Center in Atlanta and the University of Rochester Medical Center in New York researchers.

The first regimen is a dose of Moderna’s Spikevax prototype vaccine, mRNA-1273, which is authorised in the US as a booster for adults.

The second regimen is dosing with an investigational vaccine against the Beta variant, mRNA-1273.351 plus another investigational vaccine against the Omicron variant, mRNA-1273.529.

Two vaccinations administered at a gap of two months with each one containing both mRNA-1273.351 and mRNA-1273.529 vaccines is the third regimen. 

Vaccination with the investigational vaccine against the Delta variant, mRNA-1273.617.2 along with mRNA-1273.529 will be analysed as the fourth regimen.

Inoculation with mRNA-1273.529 vaccine and injection comprising Spikevax plus mRNA-1273.529 will be the fifth and sixth regimens, respectively.

The trial will assess the safety and immunogenicity of additional doses of prototype and variant vaccine candidates in trial subjects. 

Furthermore, the innate, cellular and humoral immune responses will be evaluated.

Trial subjects will be analysed for symptoms and adverse events after inoculation. The initial study data is anticipated by August this year.

The study could run for four years and may be extended to enrol 1,500 subjects in the country, UC San Diego noted.

UC San Diego School of Medicine professor Susan Little said: “The emergence of SARS-CoV-2 variants has challenged the efficacy of available preventive vaccines. 

“It’s clear that we need to learn more about how we might adapt vaccines to match circulating variants and expand and optimise immune coverage to existing and emerging variants.”