What you need to know:
- As scenarios develop and evolve, our strategy shouldn’t involve “mixing and matching” Covid-19 vaccines.
- To contextualise this, we must first understand the rationale of immunisation.
Vaccine strategy is often a delicate balance of thoughtful preparation and strong execution, with health officials forced to act with imperfect information as they prioritise scarce resources across a broad population.
As scenarios develop and evolve, our strategy shouldn’t involve “mixing and matching” Covid-19 vaccines. To contextualise this, we must first understand the rationale of immunisation.
The primary objective of vaccination is to achieve a robust and lasting immunity against a disease. This encompasses induction of an enduring immunologic memory towards the offending pathogen (antigens) and production of persistent antibodies against the antigens.
Vaccines achieve this by teaching the body to recognise an offending pathogen by introducing either a weakened part or inactivated form of a pathogen and allowing the body to develop an effective response without potential of causing a disease.
Stronger immune response
Newer vaccines use mRNA technology to provide the body with instructions on how to make spike proteins specific to the offending pathogens. This new technology has been exploited in the development of Covid-19 vaccines, including Pfizer-BioNTech and Moderna.
For some vaccines, a single dose can suffice to trigger the production of long-lived antibodies and development of memory cells. For others, multiple doses are required. The first dose primes the immune system whereas the subsequent doses induce a robust response and a vigorous production of antibodies.
Data extrapolations from clinical studies have demonstrated that Pfizer-BioNTech, Moderna, Oxford-AstraZeneca, Novavax, cornonavac and the Sputnik V vaccines provoked a relatively weak immune response when given as a single dose.
There was a stronger immune response when a second dose was added. For the Johnson & Johnson vaccine, only one dose is required. n the concept of mixing and matching the Covid-19 vaccines, the idea is not yet feasible as studies are still ongoing. Mixing and matching of drugs is not a novel idea. However, the certainty of safety and efficacy have to be backed by scientific studies.
Dr Ouma is a research fellow at the International Cancer Institute. email@example.com