From new emerging variants, multiple waves of coronavirus, to concerns over waning immunity and vaccine inequity, there has been debate on whether the mixing of COVID-19 vaccines is safe or not.
The mixing of vaccines is not a new concept in the medical field. Scientists have previously investigated the technique—which goes by the technical term heterologous prime-boost—for Ebola, tuberculosis, Influenza, Hepatitis A and other infectious diseases.
The Heterologous Prime-Boost regimen consists of DNA vaccine priming followed by recombinant adenovirus boosting to generate a strong immune system and efficacy. The two vaccines, often in a heterologous prime-boost combination, present the same antigenic components to the immune system but use different delivery systems. Heterologous prime-boost is usually considered an option due to; limited supplies of one vaccine, manufacturing delays and extreme side effects that require investigation.
According to Dr Katherine O’Brien, it is safe to mix AstraZeneca a non-replicating viral vector vaccine and any other Messenger RNA (mRNA) vaccine. mRNA vaccine uses genetically engineered mRNA to give the body cells instructions to make the S protein found on the surface of the Coronavirus. Once one is vaccinated, the immune cells make the S protein pieces and display them on the cell surfaces. This causes the body to create antibodies, and when one gets infected by the virus, these antibodies will fight the virus.
Dr Katherine O’Brien continues to say that for a better result, it is best to begin the dose with AstraZeneca then follow up with any vaccines that use mRNA technology for best results. Of the seven vaccines approved by the World Health Organization (WHO), Pfizer-BioNTech and the Moderna COVID-19 vaccines use mRNA technology.
David Masopust, an immunologist at the University of Minnesota Medical School, points out that most vaccines target the same spike protein. In theory, this means that switching vaccines should work.
There are four types of COVID vaccines; whole virus, protein subunit, viral vector and nucleic acid. These vaccines are categorized as so, depending on the technology they use.
Whole virus vaccines employed in many conventional vaccines use whole viruses to trigger an immune response, while protein subunits vaccines use pieces of the pathogen. On the other hand, nucleic acid vaccines use genetic material – either RNA or DNA – to provide cells with the instructions to make the antigen. Viral vector vaccines also work by giving cells genetic instructions to produce antigens but, unlike the nucleic acid vaccines, use a harmless virus.
Although studies show that mixing the vaccines generates a strong immune system, there might also be resultant short-term side effects such as; not feeling well or a low-grade fever after the second dose. The WHO maintains there is not enough data yet to determine whether some vaccines can be used in place of others and has not approved the mixing of vaccines. CDC (Centers for Disease Control and Prevention) also recommends that people who have received either Pfizer-BioNTech or Moderna’s COVID-19 vaccine series should only take a third dose of the same mRNA vaccine. A person should not receive more than three mRNA vaccine doses.
This story was produced by Debunk Media in partnership with Code for Africa, with support from Deutsche Welle Akademie’.