London(CNN) UK scientists have launched the world's first study examining whether different coronavirus vaccines can safely be used for two-dose regimens, an approach they say could give extra flexibility and even boost protection against Covid-19 if approved.
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Analysis released Wednesday by Oxford scientists but not yet peer reviewed suggested there could be higher efficacy with more spaced-out doses of the Oxford-AstraZeneca vaccine.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.
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.
The UK aims to have offered everyone in the four groups identified as most vulnerable -- including all those over 70 and frontline health and social care workers -- a first vaccine dose by mid-February. And Health Secretary Matt Hancock said earlier this month that vaccines would be offered to every adult in the UK "by the autumn."
Meanwhile, the vaccine rollout is picking up pace in the United States, the country that has seen the highest number of cases and deaths from Covid-19 worldwide.
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.
Israel, with a population of about nine million, has led the world with its vaccination program.
All Israelis aged 16 and over are now eligible immediately to receive a coronavirus vaccine, Health Minister Yuli Edelstein said Thursday. "Come in your masses. Take advantage of a situation which exists in almost no other country in the world. This is the only way we will beat corona -- together," the minister said in a statement.
Health Ministry figures show that 3.3 million people have received a first dose, of whom more than 1.9 million have also received their second shot.
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.
About 70% of the total coronavirus vaccine doses administrated globally have been in the 50 wealthiest countries, while only 0.1% of them have been administrated in the 50 poorest countries, according to analysis by the International Federation of Red Cross and Red Crescent Societies (IFRC).
The IFRC described the disparity as alarming and said it could result in "deadly and devastating" consequences, warning that if large areas across the globe remain unvaccinated, the virus will carry on circulating and mutating.
As vaccination programs in Europe gather momentum, Norway, Denmark, Sweden, France, Austria and Germany have all decided against recommending use of the Oxford/AstraZeneca vaccine for people over 65 due to a lack of data on that age group.
On Wednesday, Belgium recommended not administering the Oxford-AstraZeneca vaccine to people over the age of 55, citing a lack of sufficient data.
On the same day, Switzerland declined to authorize the vaccine for any age group, saying data submitted by AstraZeneca was "not yet sufficient to permit authorization" of the vaccine.
In response to Switzerland's decision, an AstraZeneca spokesperson said in a statement: "AstraZeneca has now been granted a conditional marketing authorisation or emergency use in close to 50 countries, spanning four continents, including most recently in the European Union."
"We are confident that our vaccine is effective, well-tolerated, and can have a real impact on the pandemic," the statement added.
The European Medicines Agency (EMA) -- the EU's regulator -- recommended authorizing the vaccine for use among the 27 member states without an age restriction.
In a statement made when granting conditional marketing authorization of the vaccine, the EMA said that in spite of a lack of data, protection was expected in older adults.
Meanwhile, Denmark plans to introduce a digital vaccine passport in an effort to reopen society, help businesses and ease travel, the government announced Wednesday in partnership with Danish businesses.
The scheme would initially apply to business travelers and could eventually enable all Danes to go to restaurants, conferences, music festivals and sporting events -- all of which have been restricted since a nationwide lockdown was imposed on December 15, a measure due to last until February 28.
The government hopes that by the end of February, citizens will be able to prove they have received a Covid-19 vaccination as it will be registered online.
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%.