Vaccine cocktail: Will mix and match of two Covid-19 jabs defend Coronavirus?

New Delhi, May 13: Even as COVID-19 vaccinations increase across the globe, the question arises here is whether it's possible to get people vaccinated more quickly if vaccines can be mixed and matched.

As we all know that the the first dose primes the immune system and the second dose (usually administered a few weeks after the first) boosts it.

However, the idea of using two types of vaccines isn't a new concept.

Cocktail vaccine is nothing new

Yes, you read it right, mixing two different vaccine types is known as a heterologous prime-boost vaccination, although there's a more colloquial term.

It all started in the 1990s as a strategy tested by HIV researchers. According to Dr Pierre Meulien, executive director of the Innovative Medicines Initiative (IMI), an EU and European pharmaceutical industry partnership said, 'Scientifically, this is not anything new.'' HIV researchers knew that a classical vaccine would not induce the extremely complex immunological mechanisms needed for potential protection from HIV infection.

Who is testing the cocktail vaccine theory?

Currently, in the UK, an eight-arm study assessing the mix-and-match theory is underway.

The researchers at United Kingdom's National Health Service (NHS) are conducting a study to discover the effectiveness of combining two different vaccines.

It's called the Com-COV study, and it's raising important questions, like whether this can increase or decrease vaccine effectiveness.

The two vaccines used for this study are from AstraZeneca and Pfizer-BioNTech. The trial will enrol 1,050 adult subjects aged 50 years or older who received their first dose of a Covid-19 vaccine in the past eight to 12 weeks.

Recipients will have received either the Oxford-AstraZeneca or Pfizer vaccine and will be randomly allocated to receive either the same vaccine for their second dose or a dose of Novavax or Moderna's jabs. If more vaccines are approved over the coming months, they may also be added to the trial.

How well a cocktail vaccine defends against the virus?

Mixing doses of two leading Covid-19 vaccines increased patients' side effects such as fatigue and headaches in early findings that has yet to show how well such a cocktail defends against the virus.

People who got a first dose of AstraZeneca Plc's shot followed by Pfizer Inc.'s vaccine four weeks later reported more short-lived side effects, most of them mild, researchers from the University of Oxford reported in The Lancet medical journal.

That was also true when the order of the shots was switched.

The findings were published Wednesday as correspondence, not as a full study, in The Lancet - a peer-reviewed medical journal - and came from the Oxford Vaccine Group's Com-Cov vaccine trial, which is studying the use of different combinations of approved COVID-19 vaccines for first and second doses.

"It's a really intriguing finding and not something that we were necessarily expecting. Whether or not this will relate to improved immune response, we don't know yet; we'll be finding out those results in a few weeks' time," Matthew Snape, an Oxford paediatrics and vaccinology professor who's leading the trial, was quoted saying.

It should be noted that the US Centers for Disease Control and Prevention has earlier warned against the mixing of vaccines unless there are "exceptional situations", such as a shortage of the first-dose vaccine because of production or distribution problems.

So, if you get a COVID-19 vaccine that requires two doses, you should get two of the same vaccine. Two Pfizer shots, or two Moderna shots. Not one and then the other.