Is mixed vaccination of different COVID-19 vaccines feasible?

Is mixed vaccination of different COVID-19 vaccines feasible?   Many countries in the world are facing the pressure of insufficient supply of the COVID-19 vaccine, especially in low-income countries that the problem of “a dose is difficult to find” has attracted widespread attention. The COVID-19 vaccine that has been approved globally generally requires two doses. If different vaccines can be mixed in the two vaccinations, the flexibility of vaccine supply will be greatly improved. Is this strategy feasible? The UK has launched related trials to seek answers.

The University of Oxford in the United Kingdom recently issued a communiqué stating that a clinical trial led by researchers at the school will explore the feasibility of using different COVID-19 vaccines for the first and second doses of “booster shots”. The trial received 7 million pounds (approximately US$9.68 million) in funding from the British Government Vaccine Working Group.

Researchers will recruit more than 800 volunteers aged 50 years and above from 8 test sites supported by the National Institute of Health in the United Kingdom. The effect of alternate use of vaccines jointly developed by German biotech companies. If more COVID-19 vaccines are approved in the UK in the future, they may also be included in the trial.

The trial will also evaluate the effects of the first dose and the “booster shot” inoculations at intervals of 4 or 12 weeks, respectively. By analyzing the blood samples of volunteers, researchers will monitor the impact of different vaccination schedules on the immune response of volunteers, as well as possible adverse reactions caused by the mixed use of vaccines.

Matthew Snape, the lead researcher of the trial and an associate professor at the University of Oxford, said in the communiqué: “If we can show that these vaccines can be used interchangeably in the same (vaccination) plan, it will greatly increase the flexibility of vaccine supply.

The two vaccines selected for this trial use different technical routes. Oxford University and AstraZeneca developed an adenovirus vector vaccine, while Pfizer and Biotech Technologies developed an mRNA (messenger ribonucleic acid) vaccine. . Both vaccines target the spike protein of the new coronavirus and trigger an immune response by delivering genetic material or genetic information of the spike protein to the human body.

The immunization strategy of mixing different vaccines has been used in the prevention and control of infectious diseases such as Ebola. The Ebola vaccine program of Janssen Pharmaceuticals, a subsidiary of Johnson & Johnson, was approved by the European Commission in 2020. The program is to inoculate two different vaccines successively to prevent certain types of Ebola virus infection.

Jonathan Wenxin, deputy chief medical officer of England and England, said that the COVID-19 vaccine mixed trial will give people a deeper understanding of how to use vaccines to combat this “difficult” disease. It is possible to enhance the immune response through the combination of vaccines, producing higher antibody levels and lasting longer.

Snape said that this trial may provide clues to how the COVID-19 vaccine can work against more new strains.

Before obtaining clinical trial data, health institutions in many countries are currently cautious about mixed vaccines. Mary Ramsey, the director of immunization at the Public Health Service of England, previously stated that the agency does not recommend mixing the two vaccines. After the first dose of the vaccine, the public should use the same vaccine for the second dose.

The US Centers for Disease Control and Prevention pointed out that the two mRNA COVID-19 vaccines approved in the United States cannot be used interchangeably, nor can they be mixed with other COVID-19 vaccines, unless it is impossible to determine which COVID-19 vaccine was injected in the first dose, or after completing the first dose of a certain COVID-19 vaccine After the injection, the COVID-19 vaccine can no longer be provided for the second injection and other special circumstances, and another mRNA COVID-19 vaccine can be vaccinated at least 28 days later.

Scientists are still exploring the scientific problem of mixed vaccination of different COVID-19 vaccines.

(source:internet, reference only)

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