Do I need to shoot AstraZeneca boosters in 8 weeks instead of 12 weeks?Here is the evidence so you can decide

Prime Minister Scott Morrison said yesterday Encourage people In New South Wales outbreaks, use the AstraZeneca booster for nearly eight weeks from the first shot, rather than waiting the commonly recommended 12 weeks.

“We encourage a second dose of 8-12 weeks in the first half of that period. […]..It is consistent with Doctor’s advice […] And given the risks to people from outbreaks in the area, we believe it is important for them to receive a second dose of AstraZeneca as soon as possible. “

Official health advice from ATAGI, Australia’s technical advisory group on immunity, most people still have booster shots In 12 weeks For optimal COVID protection, it can last up to 4 weeks under certain circumstances. These situations include imminent travel and the risk of COVID-19 exposure.

With ATAGI concerns Other vaccine expertsIf you do a booster shot before 12 weeks, your body will not develop enough immunity to ensure protection from serious illness.

Are you confused? This is what we have ever known.

What is the official advice?

Evidence to support Recommended 12-week gap Between the first and second shots of AstraZeneca Lancet..

The study found that less than 6 weeks from the first shot to the booster provided 55.1% efficacy (protection from symptomatic treatment). Leaving 6-8 weeks between shots increased efficacy to 59.9%, and waiting 9-11 weeks resulted in 63.7% efficacy. However, if the gap was 12 weeks or longer, the effectiveness jumped to 81.3%.

So to get the best protection from AstraZeneca vaccine, At least 12 weeks are required between the first and second shots.

We have now noticed an active outbreak of highly contagious delta variants of SARS-CoV-2 in Sydney. Therefore, you should ask yourself if it is best to aim for the highest level of protection, or if you need to aim for a reasonable level of immunity as soon as possible.

Lancet paper was not widely distributed at the time, so it did not contain data on delta variants, but this was rapidly Globally dominant variant..

Nevertheless, we know that two doses of the AstraZeneca vaccine protect against severe COVID-19 after infection with the delta mutant. Do not take once..

What is the 8-week evidence for protection from the Delta?

Morrison’s call to shoot AstraZeneca boosters for about eight weeks has not been completely successful.It’s an approach UK is using Infectious delta variant, to precede the same variant circulating in NSW.

Shortening the interval between injections of AstraZeneca has generally been shown to reduce the effectiveness of the vaccine. But what about in the context of delta variants? This is where you need to be a little careful if you want to know exactly how much your vaccine will be less effective.

Scott Morrison wants the second dose of AstraZeneca to be closer to 8 weeks. However, a recent study at Lancet found that the efficacy of AZ was reduced to 60% when administered at 8 weeks, compared to more than 80% at 12 weeks. https://t.co/IwlpatUMr0

— Chelsea Heatherington (@chelsea_hetho) July 8, 2021

Studies published in Nature We reported that a single dose of the AstraZeneca vaccine did not essentially induce delta virus neutralizing antibodies.

However, the two doses induced a neutralizing antibody response in 95% of people, but at significantly lower levels than the Alpha variant (which occurred in the United Kingdom).

Nevertheless, neutralizing antibodies to Delta were present in the majority of people after two injections. This can mean the difference between hospitalization for mild and severe illness.

This study has some limitations. First, it did not directly assess the effectiveness of the vaccine (it would require clinical trials to be conducted). Second, it used the range of intervals between the first and second shots, so it’s not possible to say exactly protection from delta strains at 8 vs 12 weeks.

However, assessing the ability of vaccinated people to neutralize the virus in the lab is a good indicator of the quality of vaccine protection. This study actually emphasized the need for booster shots to protect against delta mutants.

Therefore, the number of infections in Sydney looks ominous day by day, and coupled with the knowledge that one vaccination is of little use against the delta virus, it is possible to give two vaccinations to the arms of as many people as soon as possible. it is clear. strategy.

Two doses, even at 8-week intervals, do not provide the highest level of protection possible, but still protect many people from serious illness.

What else do I need to think about?

Weighing the strengths and weaknesses of shooting AstraZeneca boosters early is not just about weakening immunity.

I just heard that Pfizer has more shots Faster than I expected.. If anyone who already has two shots of AstraZeneca can take advantage of Pfizer’s booster shots (which is a big case), this could be a game changer.

In this case, and keep in mind that this mix-and-match approach is not officially licensed. If the immunity is not optimal with the second early dose of the AstraZeneca vaccine, it may not be so important. Pfizer boosters boost your immunity instead.

However, it remains to be seen if such a major policy shift will be in time to protect those currently blocked in New South Wales.

Takeaway message

Delta variants are highly contagious. So weeks are important, and Australia is still heavily dependent on the AstraZeneca vaccine, so for now it makes sense to reduce the time between the first and second jabs.

This is clearly the preferred method over staying unprotected for more than a month, especially if you are at high risk of infection or serious illness.

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