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Opinion | Why mRNA Covid-19 vaccines like Pfizer’s jab should be part of a long-term public health strategy

  • Our immunity to the virus wanes over time and the advantage of mRNA vaccines like Pfizer’s is they’re much easier to update than the ‘viral vector’ shots like AstraZeneca’s
  • We should still use the AstraZeneca vaccine now for over-50s – as any immunity is better than none and it will protect you from severe Covid-19, Nathan Bartlett says

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A man receives the Pfizer Covid-19 vaccine in West New York, US. Photo: AP
Last week, the chief executive of Pfizer said anyone who receives its Covid-19 vaccine will probably need to have a third dose within 6-12 months after being fully immunised, and then likely one dose every year going forward.
We’ll need these because it’s likely that, for many of us, immunity will begin to wane within that time frame. The vaccine will also need to be tweaked to cover new coronavirus variants as they emerge.
The advantage of mRNA vaccines like Pfizer’s is they’re much easier to update than the “viral vector” vaccines like AstraZeneca’s. We should still use AstraZeneca now for over-50s, but our best long-term strategy is to use mRNA COVID-19 vaccines, and therefore to develop the capacity to manufacture them here in Australia.

Immunity to coronaviruses doesn’t last

We know our immunity to different coronaviruses wanes over time. This is true for the four common cold (endemic) coronaviruses that circulate all the time – there are always sufficient numbers of people who have lost their immunity to ensure these viruses can persist and continue to cause respiratory illnesses.

Our immunity to Sars-CoV-2, the virus that causes Covid-19, also seems to wane quickly, although the rate at which this happens can be quite variable. Data suggest immunity acquired from the Pfizer shot is pretty robust for six months, but it isn’t clear how quickly our immunity is lost after that.
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