Scientists test new question on Covid-19 vaccine: Mixing different doses

Finding ways to strengthen the body’s defenses has gained new urgency due to the emergence of variants of the virus, whose vulnerability to existing photographs is not fully understood.

The researchers said the mix-and-match approach, if validated in human studies, will provide another benefit as countries struggle to inoculate their citizens: it could help reduce pressure on vaccine supply by providing doctors have more options when patients need to receive a second dose.

“Knowing that you can mix different types of vaccines depending on the availability of supplies could speed up vaccination efforts,” said Helen Fletcher, a professor of immunology at the London School of Hygiene and Tropical Medicine.

Researchers at Oxford University enroll volunteers in a study of 820 people in the UK to evaluate a one-two combination of photography developed by Pfizer Inc.

and Germany BioNTech BNTX 2.84%

SE and the vaccine developed by Oxford University and AstraZeneca PLC. The trial, partly funded by the British government, was announced on Thursday by the UK Department of Health and Welfare.

AstraZeneca said in December that it intends to test its vaccine with Sputnik V, the vaccine developed in Russia, in a human trial. That process will soon begin in Azerbaijan, the United Arab Emirates and other countries.

Immunologists said the mix-and-match strategy is a tried and tested method of improving the body’s immune response to defeat invaders. Heterologous prime-boost vaccination has been directed against other infectious diseases, including Ebola, malaria and tuberculosis, and has been used to sharpen the body’s attack on pathogens that cause some cancers and on the tumors themselves.

“I don’t see any downside to the first heterologous impulse,” said Brian Lichty, an associate professor of pathology and molecular medicine at McMaster University in Hamilton, Ontario.

By combining photos that can train the immune system to recognize and attack a pathogen in subtly different ways, the body could assemble a larger or better-equipped army to defeat any invader it encounters, according to researchers. The combined strategy could avoid the risk of a traditional two-stroke vaccine for the immune system to reject the vaccine a second time.

Sputnik V in Russia follows the idea of ​​a mix-and-match using a different viral carrier to train the immune system against Covid-19 in each of its two doses.

The trial in the UK will be the first to test a mix-and-match approach against Covid-19 using various technologies. The Pfizer and BioNTech vaccine rely on molecular couriers known as messenger RNA to carry instructions to cells. AstraZeneca’s uses a chimpanzee virus modified as a vector to deliver its payload.

“We do not have clinical data for such an approach,” said Ugur Sahin, executive director of BioNTech. Therefore, it is important to evaluate the combination of different vaccines in controlled clinical trials before simply putting this into practice. ”

Pfizer said in a statement that it recommends using the vaccine as supported by existing data from studies, but added that decisions on alternative dosing schedules are up to the health authorities. AstraZeneca said it supports the studies.

Immunologists said the mixtures of technologies are not unusual. Scientists at Oxford University in January reported in a study pending review that the combination of a different RNA-based vaccine and a viral virus vaccine generated a strong immune response in mice. Messenger RNA vaccines have been tested in conjunction with viral virus vaccines in cancers.

The purpose of the study in the UK is to test whether a mix-and-match approach works as well or better than typical practice, said Matthew Snape, associate professor of pediatrics and vaccinology at Oxford and the study’s leader.

Some participants will receive an AstraZeneca shot first, and a Pfizer second. Others will receive the opposite. Control groups will be offered the normal two-shot program of a single vaccine. The process will also look at the spacing of photos over four to 12 weeks. Preliminary results are expected in late May or early June, and participants will be closely monitored for side effects. The plan is to enroll more volunteers and test new combinations as additional vaccines gain regulatory approval in the UK, said Prof. Snape.

Researchers will regularly test participants’ blood for antibodies, infection-fighting T cells and other markers of immune system activity. They will compare those in the mixed program with those in the normal dosing regimen to detect any differences. Prof. Snape said researchers will be able to use the evidence to assess the potential effectiveness of a mix-and-match vaccination against coronavirus variants that may not be as vulnerable to standard photographs.

Mary Ramsay, head of immunization at Public Health England, a UK health agency, said the success of the study could help doctors facing blockages in the supply of vaccines. A mix-and-match strategy could help if, for example, someone could not get the second dose of the initial shot or had a bad reaction to the first.

“Indeed, implementation is much simpler,” she said.

Mene Pangalos, AstraZeneca’s executive vice president for biopharmaceutical research and development, said in a press briefing on Wednesday: “Finally, we want to understand how interchangeable these vaccines are. These are important questions because, eventually, people will use different vaccines at different times. ”

—Jenny Strasburg and Bojan Pancevski contributed to this article.

Write to Jason Douglas the [email protected]