Herd immunity is a complex subject.  I don't understand it and seemingly neither do many health experts.  There are certain axioms we can all relate to.

 

1. Some people have innate  immunity. Between 10 and 50% of people may be unaffected by a given virus. 

2. Acquired immunity is what generally nudges a population toward herd immunity.  It happens either when people are infected and recover, or through inoculation.

3. Acquired immunity regarding covid19 seems to confer 'neutralizing' antibodies. This basically means that an individual may be infected (again) but that he/she does not become ill. Nevertheless, it may be that transmission to another is possible.  This is important when one considers deploying a vaccine.

4. Viral interference- a much overlooked phenomena, but one that is likely key to seeing the back of one particular strain.  Basically, a dominant virus crowds out lesser viruses, but as it weakens the reverse happens. So, for instance, the normally dominant flu virus didn't get much of a look in this year (although social distancing may also be an explanation).

I have a feeling that I'm innately immune.  I mean this life has pretty much been fairly lucky in most respects.   

The latest news I read about AstraZeneca's vaccine is that a combination of it with the Russian Sputnik V vaccine is planned.

 

Quote

In another sign of recognition for the Sputnik jab that has been viewed with scepticism by the West, British-Swedish drugmaker AstraZeneca in December announced a clinical trial programme that would use a combination of its vaccine and the Russian one.

Source: https://www.thelocal.de/20210105/merkel-and-putin-discuss-possible-joint-vaccine-production