How Many COVID Vaccines Are We Really Going to Need?

how many vaccines will we need

With 94.2% of Australians aged 16 and over fully vaccinated, and the younger age groups catching up quickly, it feels like we’re pretty safe from the worst of the COVID-19 pandemic. Not to mention that more than half of those eligible have now received their booster shot — which, if you haven’t got yet, you should book in for now — and it feels like it should be relatively smooth sailing from here on out, provided nothing goes horribly wrong.

Last week however, Nigel Crawford, chair of the Australian Technical Advisory Group on Immunisation (ATAGI) made headlines for saying he couldn’t rule out the need for four or even five COVID-19 vaccines in order to keep Australian immunity up to scratch.

“Countries like Israel have already recommended a fourth dose and we need to look at that international data and see the impact, and what the new variant vaccines look like,” Crawford told a Senate estimates committee.

“ATAGI is constantly reviewing the evidence … that advice may change over time. It is a possibility but there’s no current recommendation to that effect.”

National Cabinet recently agreed to update the language around vaccinations, saying that three doses would now be considered “up to date,” while those who had their second shot more than six months ago would be considered “overdue.” This replaces the “unvaccinated” vs “fully vaccinated” government definitions.

So, if we could be looking at a number of booster vaccines for the forseeable future, just what does the science say on this and how many vaccines might we need before this whole thing is over with? Here’s what you need to know.

Fourth Doses and Beyond

Australian health bodies already recommend fourth doses of a COVID-19 vaccine for those who are severely immunocompromised. In the early days of the vaccine rollout, immunocompromised and at-risk people were being advised to get three doses of the vaccine before boosters were even being considered.

This all comes down to the fact that a vaccine course and vaccine boosters are different things.

A vaccine course is designed to teach your immune system how to mount a robust defence against certain viral threats. For some people, particularly those with weakened immune systems, they will require more doses of a vaccine to reach the same levels of immune response than other people. For them, three or even four doses of a COVID-19 vaccine might be needed to get their immune systems up to that level.

This differs from booster jabs, which are designed to top up your bodies immune system after it dips down from that initial peak. Research suggests that immunity to the COVID virus decreases over time following the second dose. There is also evidence that immunity not only returns to previous levels but actually increases even further with a third dose of the vaccine.

Boosters have also been shown to raise your overall immunity to the virus, even after the initial peak after the vaccine drops off. This means that your immunity remains much higher after a booster than it would otherwise.

Despite this, Israel have pressed ahead with a trial of fourth doses of the COVID vaccine to see whether this would be even more effective at creating long-lasting immunity. While their data shows that immunity increases even further, it appears to be a game of diminishing returns.

Professor Gili Regev-Yochay, a lead researcher in the experiment, said that “we see an increase in antibodies, higher than after the third dose.”

“However, we see many infected with Omicron who received the fourth dose. Granted, a bit less than in the control group, but still a lot of infections.”

This demonstrates that there is an upper limit to the effectiveness of hitting the body with the same vaccine. Omicron has changed the course of the pandemic in that it appears to have outmaneuvered vaccines to a degree. This means that we need to keep inventing new vaccines, like we do for the flu.

All of this is new terrain for science and for humanity and only time will tell whether or not we can vaccinate our way out of this pandemic. The World Health Organisation recently released a statement saying that “a vaccination strategy based on repeated booster doses of the original vaccine composition is unlikely to be appropriate or sustainable”.

Omicron and future-variant specific vaccines are in the works and could be deployed in as little as a few months time. Now that we have a working vaccine model, Pfizer and Moderna have said that they can sequence the DNA of a new variant and tweak their vaccines to fight it in a number of weeks which is lightning fast for immuno developments.

The what it all boils down to is how long our immune systems will be coming into contact with the SARS-COV-2 virus for. Vaccines are still our best tool for fighting the virus and if we continue to see waves of cases roll across the globe, it’s likely that we will need routine vaccines to combat this. These are unlikely however to be the original shots, and updated vaccines will be our answer to new and emerging variants if they become a concern.

Pandemics do not tend to stick around for very long, relatively speaking. Most appear to come and go within a few years, although some, like the plague, can return in different forms for decades and even centuries. Vaccines and our other public health measures can of course stem these outbreaks and give us the upper hand when it comes to getting them under control.

While we’re not likely to see some Middle Ages style resurgence of the plague for decades to come, updated and refreshed vaccines will likely be our best tool for dealing with new threats.

This means that the world could embark upon an even greater vaccine drive for a number of years, if the science and the logistical systems can keep up with the need. It also raises further issues of vaccine inequity as many developing countries have yet to vaccinate significant numbers of their populations with the original doses. This process could continue even as the pandemic starts to wane, as it is already very much in the process of.

So, yes, four or five vaccines could very well be needed and ATAGI have said that they will be constantly referencing the research as it emerges and updating their advice. Whether or not these will be the same four, five, or even more as the initial three remains to be seen, but we wouldn’t count on it.

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