Yarrawonga Chronicle

COLUMN BY DR CLYDE RONAN

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COVID Communique: The third shot.

So many people are now coming through the vaccinatio­n clinics for the second dose of whichever

brand of COVID-19 vaccine they have chosen or has been chosen for them.

Once the needle is in, my encouragin­g response seems to have become’congratula­tions, you have now completed your vaccinatio­n program’.

A beatific smile sweeps across the face expressing inner contentmen­t with a deed well done. Perhaps they just want to be free again and see vaccinatio­n as the ticket. Free to go to a grand final, hopefully at the MCG rather than exotic and distant locations. Free to go somewhere, anywhere.

The only reason that Perth could put on the game so successful­ly was the close attention to detail, and safety, and even then there have been after game issues with miscreants, from Victoria of course. Many others stayed at home to misbehave. The Demons won because they played better football on the day. Don’t over read it. Political machinatio­ns, money, board room meetings, celebrity spruiking - none of this would have worked without carefully planned safety measures.

It was good to have the game in Perth, since it is a national competitio­n. It might have been better with just the WA teams in it, if that could have been organised.

Some punters ask me about what happens next, meaning a third shot. They have probably been watching too much TV to have even thought about it fully, but no one knows the answer. And a third shot is not the same as a booster which comes much later. Our regulatory authoritie­s - TGA and ATAGI - are working on it which means waiting to see what happens elsewhere in the world and studying what science tells us. Then we will know what to do.

A third shot is being advised in some places for those at higher risk such as the elderly (eg. Joe Biden).

A booster may be advised to rejuvenate our immune system if there are fading antibody levels later on. Then there is the question of whether these supplement­ary shots should be with a different type of vaccine’mix and match’-which may provide some extra theoretica­l benefits.

Should it be with the Novavax which we have contracted to purchase in breathtaki­ng quantities, or the AZ that nobody wants?

A contra view was offered by Dame Sarah Gilbert, the team leader from Oxford that developed the AZ vaccine. She said that it might not be necessary but wait for the evidence. I have been telling people that there probably will be, and narrowed it down to ‘next year’, but what would I know? We have to be prepared to wait as research pops out of the test tube and into population studies to reveal the truth.

This brings me to the significan­ce of the anamnestic response to immune challenge. Keep reading please. We have been overly reliant on antibody response to vaccinatio­n, because that can be counted by numbers, as a measure of presumed protection against germs such as SARS-CoV-2 (COVID-19).

Sometimes people don’t provide an antibody response to vaccines, or anything that can be measured at all, but mysterious­ly mount a defence when it becomes necessary, through someweird mechanism of immunologi­cal awakening.

So, if our antibody levels fade after a preliminar­y two dose course, all is not necessaril­y lost because our dormant immune system may emerge from hibernatio­n if challenged by an illness, or a third or subsequent vaccine booster dose. Welcome to the anamnestic response. And a future vaccine may be so different and so specialise­d that it can help to protect us against new and as yet unidentifi­ed variants of coronaviru­s. mRNA vaccines such as Pfizer and Moderna have that potential for easy adaptabili­ty.

I have written before about killer T-cells, which attack other cells already infected with virus, in a search and destroy mission. The immune system is like a defence force with weaponry including fighter jets. T cells are not so easy to measure in terms of capability. Immunology is a very exciting discipline, and much more engaging than Star Wars or the SpaceX Starship exploits.

Maybe we should just concentrat­e on getting the world vaccinated to a basic level first (while the scientists keep working in their labs on the next great imperative). Go science.

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