Will we need a booster shot?
In an excellent article from the Doherty Institute, Nobel Laureate Professor Peter Doherty describes that a booster shot may be “a good idea” with any of the COVID vaccines, or indeed after having been infected with SARS-CoV-2.
He cites the case of the 33 year old man from Hong Kong who has recently been proven to have been infected twice with SARS-CoV-2. This patient was quite symptomatic with his first infection, whereas the second infection was asymptomatic. It is thought that the patient’s immunity had waned sufficiently to allow him to be re-infected.
Professor Doherty describes how the “one-shot” strategy was used when the measles vaccine was first introduced in 1968, however there were outbreaks in the USA by 1981.
“It turned out that children maintained their immunity while there was still enough measles virus circulating in the community to give them a mild reinfection.” he wrote, “the problem was overcome by giving a measles booster.”
The concept of “prime-boosting”
Prime-boosting is the concept of using different vaccines sequentially to deliver the same antigen to elicit a maximum T-cell memory (cellular immune) response.
An article in “Trends in Immunology” reviews the topic. It notes that while there have been many vaccine successes, there are other diseases such as HIV, TB and malaria which “resist the humoral (antibody-based) immunity that is characteristically generated by traditional vaccines.”
“Over the past few years, significant effort has been directed to promote potent cellular immunity to these pathogens. One effective technique is the ‘prime-boost’ strategy which involves priming the immune system to a target antigen delivered by one vector and then re-administering the antigen using a different vector.”
The logic behind prime-boosting is that the subject develops some immunity to the first vector and this inhibits “robust antigen presentation” when the same vaccine is used to boost.
An example in the context of COVID vaccination may be giving the Oxford vaccine, which uses an adenovirus to deliver the spike antigen, and then boost possibly with a molecular clamp vaccine, such as the one being developed by the University of Queensland.
DR DOUG QUARRY, Group Medical Director, Health Intelligence