A major trial in the UK that looks at whether Covid vaccines can be mixed and matched has been extended to include the Moderna and Novavax jabs.

The Com-Cov study has been investigating the immune responses from people given a dose of the AstraZeneca vaccine followed by the Pfizer jab, and vice versa, according to reports.

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Now the trial, led by the University of Oxford, will be extended to include the Moderna and Novavax jabs.

The additional study will recruit adults aged over 50 who have received their first does in the past eight to 10 weeks.

The volunteers, who will have received an AstraZeneca or Pfizer dose, will be randomly allocated to receive either the same vaccine for their second jab, or a dose of Moderna or Novavax.

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Researchers will be keeping tabs on any adverse reactions to the different mixture of vaccines, and how the immune systems responds.

The results will be compared with previous findings when looking at a person being immunised against Covid-19 with just one type of vaccine.

The University of Oxford said the intent of the study was to show that mixing vaccines is not substantially worse than not mixing vaccines.

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If the study shows promising results, medical regulators would formally assess the safety and efficacy of any new vaccination regime before it would be rolled out to patients.