UK trial experiences with mix of Covid vaccines

LONDON – A trial is being launched in the UK to determine whether using different Covid-19 vaccines for the first and second doses works in an attempt to make national immunization schedules more flexible.

The trial, led by the University of Oxford and managed by the National Immunization Scheduling Assessment Consortium, will assess the feasibility of using a different vaccine for vaccination from ‘first’ to initial vaccination. of follow-up “reminder”.

It is hoped that the study will help policymakers understand whether mixing different Covid vaccines might be a viable route to increase the flexibility of vaccination programs and whether it might even offer better protection.

“If we show that these vaccines can be used interchangeably within the same schedule, this will greatly increase the flexibility of vaccine administration and may provide clues as to how to increase the extent of protection against the new strains. virus, ”Matthew Snape, chief trial researcher and associate professor of pediatrics and vaccinology at the University of Oxford, said Thursday.

The trial, officially known as the “COVID-19 Heterologous Prime Boost study” but has been dubbed the “Com-Cov” study, will recruit more than 800 volunteers aged 50 and over in England to evaluate the four combinations different booster vaccinations.

He will test a first dose of the Oxford-AstraZeneca vaccine followed by a booster with either the Pfizer-BioNTech vaccine or another dose of the Oxford-AstraZeneca vaccine. Research will also focus on a first dose of the Pfizer-BioNTech vaccine followed by a booster with either the Oxford-AstraZeneca vaccine or another dose of the Pfizer-BioNTech vaccine.

These will be evaluated at two different dosage schedules: at a four week interval to give an early intermediate reading of the data, and at a 12 week interval. The latter dosing interval is the current UK vaccination policy: a delay in the second dose means more people can get their first vaccines earlier from a limited stock of vaccines.

Although the policy was seen as controversial, with some experts fearing that it would make vaccines used in the UK less effective; So far, only applicants from the University of Oxford-AstraZeneca and Pfizer-BioNTech are being used, with the Moderna vaccine due to be added to the basket of used vaccines later in the spring.

However, the University of Oxford on Wednesday published a study in which it showed that a 12-week delay between the first and second dose of the AstraZeneca vaccine increases the effectiveness of the vaccine.

Researchers found that the vaccine was 76% effective in preventing symptomatic infection for three months after a single dose and that the rate of effectiveness increased to 82.4% when there was at least a 12-week interval. before the second dose. When the second dose was given less than six weeks after the first, the efficacy rate was 54.9%.

In the latest “Com-Cov” study, researchers will collect blood samples from trial volunteers and monitor the impact of different dosing regimens on participants’ immune responses, as well as looking for possible additional adverse reactions to them. new combinations of vaccines.

The study will run for 13 months and was supported by £ 7million ($ 9.5million) government funding from the Vaccine Task Force, which was set up by the UK last April to coordinate efforts to research and produce a vaccine against the coronavirus.

Professor Snape said the study was “extremely exciting”, adding that “it will provide vital information for vaccine deployment in the UK and around the world”.

Wealthier countries are working to vaccinate as many people as possible under national lockdowns, aimed at limiting the spread of infections and preventing hospitals from being overrun, hurting economies.

The UK has been hit hard by the pandemic and has seen cases increase in the winter, aided by a more virulent variant of the virus that has emerged in south-east England and has now become a dominant strain in the country.

The UK currently has the fourth highest number of cases in the world, with more than 3.8 million confirmed infections, according to a Johns Hopkins University tally, and has recorded 109,547 deaths.

The UK government quickly pre-ordered coronavirus vaccines from various manufacturers early last year and approved the vaccines currently in use. Its immunization program has been widely praised for its agility and reach, and it is on track to have immunized 15 million people across its four main priority groups, including health and care workers, the elderly and those over 70 and anyone deemed to be clinically extremely vulnerable, by mid-February.

The latest government data, as of Wednesday, shows just over 10 million people have received their first dose of the vaccine, and just under 500,000 have also received a second dose. The Oxford-AstraZeneca vaccine, which is produced in Great Britain, forms the bulk of the UK’s immunization program.

Deputy chief medical officer and lead study leader Professor Jonathan Van-Tam said research may even show alternate vaccines could increase the level of antibodies needed to fight a potential Covid-19 infection.

“It’s even possible that by combining vaccines, the immune response could be enhanced, resulting in even higher levels of antibodies that last longer; unless it’s evaluated in a clinical trial, we just won’t know. This study will give us a better understanding of how we can use vaccines to stay abreast of this nasty disease, ”he said.

British Vaccines Minister Nadhim Zahawi told the BBC on Thursday that, for now, the country’s immunization program will continue as normal: “At the moment we will not change anything at all,” Zahawi told the program. ” Today “.

“If you had a Pfizer BioNTech vaccine for your first dose, you will have a Pfizer BioNTech vaccine for your second. If you have received Oxford-AstraZeneca, you will have Oxford-AstraZeneca for your second dose.”