‘I’ve had my vaccine - how well will it protect me and for how long?’
What are the chances that my vaccine will not work?
The prospects of vaccines failing to trigger immune responses are dismissed as remote by scientists. “If a vaccine has not been properly refrigerated that might pose problems but doctors take great care to ensure that doesn’t happen,” said Prof Helen Fletcher at the London School of Hygiene & Tropical Medicine. “Frankly the only other way to get a failed reaction is for the doctor to miss your arm – which isn’t likely.”
If I have only a few Covid antibodies does that mean I am not protected against the disease?
A lack of antibodies does not signify lack of immunity, scientists stress. Vaccines also trigger T-cells that can attack the Covid virus. However, the latter are far harder to detect – though both play vital defence roles. “We now think T cell responses are probably protecting us against severe disease while antibodies are probably preventing transmission to others,” said Prof Eleanor
Riley of Edinburgh University.
Exactly what protection does a vaccine with 95% efficacy provide?
This figure means that people in a clinical trial who were given a vaccine had a 95% reduction in risk of getting the disease. To put this statistic a different way, it means that unvaccinated people in the clinical trial were 20 times more likely to get Covid-19.
How long will a vaccine’s protection against Covid-19 last?
This is a major issue that is now being studied carefully by scientists though they warn it may take some time before they can definitively say how long vaccine protection will last. “It might well be that we can go beyond 12 months and into next year without facing problems of fading protection although it is more likely we will have to start boosting with a third vaccine shot towards the end of next year,” said Fletcher.
How will the appearance of virus variants affect vaccine programmes?
Apart from the length of protection provided by current vaccines, the appearance of virus variants that reduce their efficacy is also a concern and could further reinforce the need for more vaccine campaigns later this year. “It’s early days,” said Riley. “However, several companies are already working on vaccines that could address variation although that work will take months. Nevertheless, they would be ready by autumn – if we need them.”
What sort of vaccines will be available in autumn?
Apart from the Pfizer and Oxford vaccines, Britain has signed up for supplies of tens of millions of doses of Moderna, Novavax and Valneva vaccines. These could be given to provide wider protection. Alternatively, new variant versions of current vaccines could be developed and might even be given with flu vaccines as joint inoculations, a regime that might be repeated every
winter.
• This article was amended on 28 February 2021 to correct the answer to the question about vaccine efficacy.