The short answer is 'yes'. If you knock it on the head the first time then that's fine but if you don't...

DW: The problem with weak vaccines

When weak vaccines are used, however, or the second dose is delayed for too long, the vaccine has the exact opposite of the desired effect. That's what Pennsylvania State University virologist Andrew Read warns against. In 2001, his research with poultry viruses led him to the conclusion that low-efficacy vaccines could even promote the development of more dangerous virus strains.

So we need to think it through. We don't want another situation with health professionals over-proscribing drugs and making things worse.

AstraZeneca's efficacy is low - it's being dumped on developing countries. It's long term side-effects are unknown.

Do the experts really know what they're doing? Or is it all about money and not losing face?