Booster jags: Why AstraZeneca isn’t used as a Covid booster vaccine - and if you can have a Pfizer booster after an AZ jab
The Scottish Government is continuing to roll out its coronavirus booster vaccination programme across the country, with a quarter of the population having now received a booster or third dose of a vaccine.
On Tuesday, the First Minister Nicola Sturgeon said that booster vaccinations will soon be added to Scottish vaccine passports – with these potentially set to be extended to avoid chances of a Christmas lockdown.
The booster jag, intended to give those who have been fully vaccinated with a coronavirus vaccine more resilience against the virus as it continues to mutate and spread across the world, is currently being offered to carers, NHS staff, those who are immunocompromised and people over the age of 50.
Here’s why AstraZeneca is not used for booster vaccines – and what this means for those who have received AstraZeneca jabs.
What are Covid booster jabs?
Covid booster vaccinations are being used to offer an extra layer of protection against coronavirus six months after having your second Covid vaccine, with the UK Government announcing in September that it would be offering booster jabs to Brits in response to Joint Committee on Vaccine and Immunisation (JCVI) advice.
The JCVI called on the UK Government to administer booster vaccines to roughly 30 million vulnerable citizens in the UK after it was discovered that potent Covid variants like Delta had helped to slightly diminish the efficacy of vaccinations six months after receiving a second dose.
The booster vaccine itself comprises a dose of the Pfizer/BioNTech vaccine, or half dose of Moderna, and is administered alongside the flu jab for some groups in Scotland.
Why is AstraZeneca not used for booster vaccines?
While AstraZeneca was one of the three vaccines offered to Brits during the Covid vaccination programme, it is not among the vaccines being commonly used for booster jabs.
According to the JCVI, the reason for AstraZeneca not being used as a booster is due to the fact that it is not an mRNA vaccine - unlike Pfizer/BioNTech and Moderna.
Typically, flu jabs and many similar vaccines we receive will encourage our immune response by injecting a weakened germs or parts of a virus into our bodies to trigger an immune response.
But mRNA vaccines, or messenger RNA vaccines, are those which instruct our bodies to reproduce the SARS-CoV-2 spike protein and break this down through a direct immune response.
These kinds of vaccines have been used in trials for cancer treatments and all sorts of health solutions for years, but have only been fully trialled and licensed for the first time for Pfizer and Moderna’s Covid vaccines.
The JCVI advised that the Pfizer/BioNTech vaccine be prioritised for booster vaccinations in the UK, with a half dose of Moderna available as an alternative, after the UK’s COV-BOOST trial found that the Pfizer vaccine produced the strongest booster response out of seven possible options.
Who will still receive an AstraZeneca booster vaccine?
The UK Government and JCVI said that while the Pfizer/BioNTech vaccine will be predominantly used in its booster vaccine programme, the Oxford-AstraZeneca vaccine will be made available to those who are allergic to any ingredients in the Pfizer/BioNTech or mRNA vaccines.
It may also be used if you previously received two AstraZeneca Covid vaccinations previously.
Can I have a Pfizer or Moderna booster jab if I received AstraZeneca vaccines?
The JCVI states that the Pfizer booster jab is the preferred option for booster vaccinations regardless of the vaccine received in the first round of Covid vaccination.
A statement issued by the JCVI in September said: “mRNA vaccines provide a strong booster effect, regardless of whether the primary course was with the Pfizer-BioNTech (BNT162b2/ Comirnaty®) or the AstraZeneca (ChAdOx1-S/Vaxzevria®) vaccine.
"These results are consistent with those from other studies that examined the effect of half dose (50µg) Moderna (mRNA-1273/Spikevax®) vaccine following primary courses of full or half doses of Moderna mRNA-1273 vaccination.
"A half dose (50µg) of Moderna (mRNA-1273/Spikevax®) vaccine given as a booster was found to cause a similar level of local and systemic reactions to vaccination (injection site pain and headache) compared to a full dose of Moderna (mRNA-1273/Spikevax®) given as a second dose.”