Our first question comes from Melissa Whiffin.
Melissa asks: Do all the vaccines just reduce the severity of symptoms rather than stop you catching the virus?
And if so, why is it required by those that have already survived the virus or are expected to have no symptoms or at worst a severe flu indicating the immune system is effective without outside help?
Here’s what Paul Nuki, our Global Health Security Editor, has to say:
The original trials for the vaccines just looked at symptomatic disease so we are still learning – from real world data – about the extent to which they block asymptomatic infection. Early indications are they reduce it to an extent but to what extent is still unknown. It could also vary depending on the variant of the virus you are exposed to.
The AstraZeneca jab, for instance, was found in one study to be only 10 per cent effective at stopping infection with the South African variant. On natural immunity, it’s important to note that this will fade with time, so someone who caught the virus nine months ago may not have good natural immunity today. Vaccines, it is hoped, will give longer lasting immunity but some may turn out to be better than others in this respect, and even then the immunity they give may not last forever.