Australia is using a 12 week interval for the astra Zeneca, new info shows it gives greater immunity.
Originally I think it was tested with a four week interval, but I think the UK wanted to get one shot in as many arms as possible as 65% immunity after 1 shot.
they found 12 weeks is not only a better immune response but they can vaccinate more people.
It will probable lessen deaths and severe covid regardless of the strain, but may not be as effective.
I expect your third booster will be a different type which will give wide spread coverage, just speculation.