The UK is launching a trial to explore the mixing of vaccines can be combined. Some, like Russia’s Sputnik vaccine, already combine two different types of vaccines, but these were specifically designed and tested to work together.
Current guidance in the UK says that anyone who receives a Pfizer-BioNTech or Oxford-AstraZeneca vaccine dose should get the second dose of that same vaccine. Only in exceptional circumstances such as not knowing what vaccine was given will a different vaccine be administered.
The main aim was to enhance logistical flexibility. The Oxford/AstraZeneca, Johnson & Johnson and Novavax vaccines can all be stored at normal refrigerator temperatures, while the Moderna vaccine must be stored at -20C, within normal freezer range, and Pfizer/BioNTech’s vaccine needs an ultra-cold -70C. Not requiring a second dose of the same vaccine could ease up storage requirements.
However, with previous vaccines, mixing different vaccine types worked and even strengthened their overall effectiveness. Some Ebola immunisation programmes, for example, combine two different vaccines to achieve greater protection.
The trial will comprise some 800 participants aged 50 or older, receiving a combination of Oxford/AstraZeneca and Pfizer/BioNTech in either order.
Some vaccines that work by using a virus to deliver the antigens, and there is some evidence to suggest that the immune system starts to focus on the viral delivery system instead of the antigen. Thus, combining vaccines will keep the immune system’s attention on the antigens.
Chief investigator, Prof Matthew Snape from the University of Oxford, said the “tremendously exciting study” would provide critical information for vaccine rollouts.
Animal studies have shown “a better antibody response with a mixed schedule rather than the straight schedule” of vaccine doses, he said.
“It will be really interesting to see if the different delivery methods actually could lead to an enhanced immune response [in humans],” he said, “or at least a response that’s as good as giving the straight schedule of the same doses”.
Source: BBC News
