More than 7 million Australians have received their first COVID-19 vaccine, but it's likely to take until April 2022 before the majority of the adult population is fully vaccinated.
Key points:
- Research has shown that a 12-week interval between AstraZeneca vaccine doses offers optimal protection
- The UK has cut the wait between doses down to eight weeks in order to tackle the fast-spreading Delta variant
- Getting a second dose earlier offers less protection, but could be a way to get more people vaccinated sooner
The federal government's expert vaccine advisory panelcurrently recommends that the Pfizer vaccine is given three weeks apart, while people who've had their AstraZeneca jab are advised to wait 12 weeks before getting their second dose.
But in some countries, including the UK, health authorities are shortening the interval between AstraZeneca vaccines in a bid to accelerate their vaccination programs.
In Australia, where more than 4 million people have received at least one dose of AstraZeneca, could reducing the wait time between vaccines help speed up our lagging rollout?
And would that compromise the effectiveness of the vaccines?
Let's take a look.
What are the current recommendations?
Unsplash: Mika Baumeister
)The Australian Technical Advisory Group on Immunisation (ATAGI) currently recommends people who have received their first dose of the AstraZeneca vaccine should wait 12 weeks to get their second, with a minimum wait of four weeks.
This is in line with research that has shown that a 12-week wait between doses provides optimal protection against COVID-19.
A study published earlier this year in The Lancet found that a single dose of AstraZeneca is 76 per cent effective in the first 90 days.
Receiving a second dose 12 weeks or more after the first can kick this protection up to 82.4 per cent.
But this efficacy dropped to around 55 per cent if the second jab was given less than six weeks after the first, the study found.
Why have some countries reduced wait times?
As the highly contagious Delta variant takes hold in many parts of the world, including the UK, health authorities have decided to reduce the interval between AstraZeneca vaccines from 12 weeks to eight weeks for people aged 40 and above.
"The Delta variant has changed the environment for vaccines in the UK … We now know that two doses of vaccine are very much better than one dose for protection against infection with the Delta variant," UK deputy chief medical officer Jonathan Van-Tam said.
Clinical epidemiologist Terry Nolan said the emergence of the Delta variant and the sheer number of COVID-19 cases in the UK meant they urgently needed to get as many people fully vaccinated as possible.
Getty Images: Peter Byrne — PA Images/Contributor
)"Their concern was that the Delta variant was much more transmissible and possibly more severe and more likely to result in hospitalisation," said Professor Nolan of The Doherty Institute.
"They wanted to bring forward the protection because their [COVID] numbers were starting to increase again."
Is there a sweet spot?
While research shows the AstraZeneca jab generates the strongest immune response when given 12 weeks apart, Professor Nolan said reducing that interval to eight weeks only reduced that protection modestly.
"There's actually a curve that shows the optimisation of protection as you get to 12 weeks," he said.
Kylie Quinn, a vaccine expert at RMIT, agreed that giving the AstraZeneca jab at eight weeks still provided "pretty decent levels of protection".
But she said any decision to reduce the recommended interval between vaccines should be based on what a country's goal is.
If building the highest protection possible in every individual is top priority, then waiting longer to receive the second dose is the better option, Dr Quinn said.
But in places where there are high levels of community transmission, such as the UK, fast-tracking second doses may be a better option.
"It makes good sense to try and build people's immunity up to a decent level quicker, and perhaps accept a slightly lower level of antibody responses," Dr Quinn said.
"It's [about] understanding those trade offs and understanding what's best for that particular population."
Should Australia change its guidance?
In Australia, just seven per cent of the adult population has been fully vaccinated against COVID-19.
Professor Nolan said cutting down the time between AstraZeneca doses could help more people get vaccinated sooner, particularly with the threat of outbreaks growing during winter.
"The best counter to that would be to get as much of the population protected with vaccines as quickly as possible," he said.
"The argument was being made early that there's no race, we don't have to hurry. That was wrong."
Professor Nolan said another option to get more of the population at least partially vaccinated was to consider extending the interval between the first and second doses of Pfizer.
Getty Images: Lisa Maree Williams/Stringer
)That would mean available supplies could be used to give more people a first dose, rather than giving people who are already partially-protected a second dose.
Research has shown that just one dose of Pfizer offers up to 85 per cent protection.
"The data shows that at least one dose of protection is actually excellent," he said.
"If you deferred the due date for the second dose until a time when more Pfizer vaccines were available, what you buy is the level of not perfect, but very good, protection for a much larger percentage of the population."
Dr Quinn said that because Australia doesn't have significant levels of community transmission, there was rationale behind sticking to the recommended vaccine intervals in order to achieve maximum individual protection. But, she added, there was also an argument for having more flexibility in our dosing regime.
"Some people may be really motivated to have higher levels of immunity quicker … they might have family members who are particularly vulnerable and just want to make sure they have protection."
What about mixing and matching vaccines?
While Australian health authorities have decided against mixing and matching COVID-19 vaccines, the early data looks promising.
A UK study published this week involving 830 volunteers over the age of 50 found that a first dose of AstraZeneca followed by a second dose of Pfizer (four weeks later) resulted in better protection than two shots of AstraZeneca.
"[It] produces a very, very good immune response, at least as good or possibly better than if you had the first and second doses of Pfizer, and much better than if you had the first and second AstraZeneca doses," Professor Nolan said.
In addition to producing a better immune response, mixing vaccines could lead to other benefits, Dr Quinn said.
But Professor Nolan said that at the moment, mixing vaccines could actually slow down Australia's vaccine rollout even further, due to the extra demand for Pfizer shots.
"Until there is more Pfizer vaccine or Moderna vaccine, that prospect of mix and match is probably not going to help the Australian situation."
"wait" - Google News
July 05, 2021 at 02:00AM
https://ift.tt/3jMg8FR
How long should you wait to get the second AstraZeneca jab? - ABC News
"wait" - Google News
https://ift.tt/35qAU4J
https://ift.tt/2Ssyayj
Bagikan Berita Ini
0 Response to "How long should you wait to get the second AstraZeneca jab? - ABC News"
Post a Comment