ATAGI and some other vaccine experts worry that if you get a booster vaccine before 12 weeks, your body will not produce enough immunity to protect against serious disease.
What is the official advice?
The advice to have a 12-week gap between the first and second vaccines of AstraZeneca came from a study published in The Lancet. The study found that less than six weeks between the first vaccine and the booster vaccine protects against symptoms of the disease by 55.1 percent. Between these six to eight weeks, this capacity increases to 59.9 percent and between nine and 11 weeks to 63.7 percent. If the interval between vaccines is 12 weeks or more, this efficiency increases to 81.3 percent. Therefore, to get the best protection from the AstraZeneca vaccine, you need to keep a gap of at least 12 weeks between the first and second vaccines.
There have been several cases of the highly contagious delta form of SARS-CoV-2 in Sydney. So we need to ask ourselves whether it is better to have a higher level of protection or do we need to get some degree of immunity as soon as possible. The Lancet study does not include data on the delta form because there were no cases at that time, but now its cases are increasing worldwide. We do know that two doses of AstraZeneca protect against serious illness after being infected with the delta form, while one dose does not.
What evidence is there of a gap of eight weeks for defense against the Delta format?
Morrison’s appeal to have AstraZeneca’s booster vaccine in about eight weeks is not entirely surprising. The UK is also using the same approach to deal with the highly contagious delta pattern, and cases of the same pattern are on the rise in New South Wales. We know that shortening the spacing between AstraZeneca vaccines generally results in a reduction in the effectiveness of the vaccine. But what can be said about the delta form?
A study published in the journal ‘Nature’ said that a single dose of AstraZeneca vaccine does not necessarily produce antibodies that kill the delta virus. Two doses produce antibodies in 95 percent of people. This study also has some limitations. First, it did not directly assess the effect of the vaccine (this requires clinical trials). Secondly, it used many gaps between the first and second vaccine, so we cannot say anything for sure. It can be said that a single dose of the vaccine is ineffective against the delta form as cases of infection increase in Sydney and it is clear that giving both doses to as many people as possible is one strategy. Giving two doses in eight weeks will not provide a high level of protection against the corona virus, but it will prevent falling seriously ill.
What else do I need to think?
Talking about the merits and demerits of getting the AstraZeneca booster vaccine early, decreased immunity is not the only thing to consider. We just heard that more vaccines from Pfizer are likely to come soon. If Pfizer’s booster vaccine becomes available to people who have already taken both doses of AstraZeneca, it could prove important. Remember that there is no official approval for this type of vaccine. It may not matter much if the second dose of AstraZeneca vaccine does not give you as much protection. Pfizer’s booster vaccine will boost your immunity.
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The delta form is highly contagious. That’s why weeks matter and Australia’s reliance on the AstraZeneca vaccine makes sense for the time being to reduce the gap between the first and second doses. It is clearly okay to stay away from the corona virus for another month, especially when you are at high risk of contracting the infection or falling seriously ill.