Can you mix vaccines? UK trial aims to find out - CNN

Participants in the 13-month study will be given the Oxford/AstraZeneca and Pfizer/BioNTech vaccines in different combinations and at different intervals, the UK Department of Health and Social Care said in a news release.

"If we do show that these vaccines can be used interchangeably in the same schedule this will greatly increase the flexibility of vaccine delivery, and could provide clues as to how to increase the breadth of protection against new virus strains," said Matthew Snape, chief investigator and associate professor in pediatrics and vaccinology at the University of Oxford.

Enrollment in the UK government-funded study is currently underway and preliminary results are expected over the summer, the news release said.

The current vaccine dosing regimen for the general public will remain unchanged in the UK, it said. But should the study show promising results, the government may consider revising the recommended vaccine regimen.

The study will also seek to determine if vaccination is more effective with a four-week or 12-week gap between the two doses. More than 800 people are expected to take part in the trial and will begin receiving their shots by mid-February.

Analysis released Wednesday by Oxford scientists but not yet peer reviewed suggested there could be higher efficacy with more spaced-out doses of the Oxford-AstraZeneca vaccine.

Minister for Covid-19 Vaccine Deployment Nadhim Zahawi said the new trial would provide vital evidence on the safety of the two shots when used in different ways.

"Nothing will be approved for use more widely than the study, or as part of our vaccine deployment programme, until researchers and the regulator are absolutely confident the approach is safe and effective," he said.

Jonathan Van-Tam, England's deputy chief medical officer, said that given the challenges of rolling out mass vaccination of populations and "potential global supply constraints," there were advantages to having data to support a more flexible immunization program, if needed and approved by the regulator.

"It is also even possible that by combining vaccines, the immune response could be enhanced giving even higher antibody levels that last longer; unless this is evaluated in a clinical trial we just won't know," said Van-Tam.

Currently, official guidance from the UK's Joint Committee on Vaccination and Immunisation states that the second dose should be with the same vaccine as for the first dose. "Switching between vaccines or missing the second dose is not advised as this may affect the duration of protection," it adds.

However, in certain circumstances where a patient attends a site for a second vaccination and what was given for the first dose is either unknown or unavailable, it is "reasonable to offer one dose of the locally available product to complete the schedule," guidance states, particularly if the individual is at high risk of infection or is unlikely to attend again.

The US Centers for Disease Control and Prevention (CDC) and the World Health Organization do not currently recommend interchanging coronavirus vaccines, since no data is currently available that examines whether doing so would still provide the same level of protection.

Successful vaccination rollout

The UK has been one of the world's worst-hit nations during the pandemic, with among the highest confirmed Covid-19 deaths proportionate to its population.

It has, however, shown global leadership by launching a successful vaccination program, becoming the first country to approve and administer a clinically tested vaccine. More than 10 million people in the UK, around 15% of the population, have received at least one dose to date.

Other countries are struggling to overcome problems with vaccine supply and distribution. Last week, a war of words erupted between the European Union and AstraZeneca after EU officials said they had been told by the company that it intended to supply "considerably fewer" doses in the coming weeks than had been agreed because of production problems.

And South America accounts for roughly 15% of the world's reported Covid-19 cases, but less than 3% of the global vaccine doses administered so far, according to data collected by Oxford University.

Meanwhile, the vaccine rollout is picking up pace in the United States.

Nearly 34 million doses of Covid-19 vaccine have been administered so far in the US, according to data published Wednesday by the CDC. That means just over 8% of the US population -- more than 27 million people -- have now received at least one dose of the vaccine, and about 6.4 million people have been fully vaccinated, CDC data shows.

At the current rate, every adult in the US could be fully vaccinated in about a year. Assuming 75% of US adults must be fully vaccinated to achieve herd immunity, the US could reach this threshold by around Halloween.

The UK aims to have offered everyone in the groups identified as most vulnerable -- including all those over 70 and frontline health and social care workers -- a first vaccine dose by mid-February.

Health Secretary Matt Hancock said earlier this month that vaccines would be offered to every adult in the UK "by the autumn."

Pandemic handling judged

A new poll from the Pew Research Center, conducted in November and December, finds widely differing views in the four nations surveyed -- the United States, Germany, France and the UK -- about their own country's handling of the coronavirus pandemic.

Just 41% of Americans approve of how their country is handling the pandemic, a new survey from the Pew Research Center finds. Asked simply whether the country is doing a bad or a good job, 58% of those polled came down in the "bad" category.

Meanwhile, Germans overwhelmingly approve of their country's handling of the pandemic, with 77% rating it as "good." In France, 54% of those polled approve of their country's handling and in the UK, 48% did.

The survey of 4,000 adults across the four countries also found that 74% of Americans say the pandemic is affecting their everyday lives a great deal or a fair amount, up from 67% in June.

"Only in Germany do fewer than half of those surveyed say the coronavirus has changed their life, while 52% say their life has not changed much or not changed at all," Pew said.

But people in all four countries are optimistic about future pandemics. In the US, 67% say they feel optimistic about the country's ability to handle future crises. In Germany, 77% do, while in the UK that figure stands at 68% and in France at 60%.

CNN's Laura Smith-Spark wrote in London and Christopher Rios reported from Atlanta. CNN's Michael Nedelman contributed to this report.

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