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The news that the Oxford/AstraZeneca vaccine is less protective against the South African variant of Covid-19 has caused a lot of concern. But before we start worrying, we should first be clear about the details. While the current vaccine has less efficacy against the South African variant, it offers only slightly less protection when used on the variant first identified in Kent. And it is still thought to be likely that the vaccine will protect against serious disease caused by the South African variant.
This is an important detail. The current death toll in the UK is frighteningly high. Thousands of people are in hospital being treated for Covid-19, and many more are dying at home. Our first priority is to ease the death toll and the number of hospital admissions, which are overwhelming the NHS. If the Oxford/AstraZeneca vaccine is still effective at preventing serious disease caused by the South African variant, then it should help with both of these things. A vaccine that prevents serious illness is more than adequate for the time being to get the pandemic under control.
In general, vaccines of all types are most effective at preventing severe illness and less effective at preventing mild to moderate illness. Vaccines work by preparing the body’s immune system so that if it encounters the virus, it recognises it immediately. After a person has been vaccinated, they may have sufficient neutralising antibodies circulating in their bloodstream to destroy a virus before it can cause infection. If they don’t, they will have memory cells, which can rapidly produce the necessary antibodies. Vaccination also primes the immune system to produce other responses, such as T cells, which destroy cells infected by the virus. This immune response may take a little time, in which the virus might start to cause a few symptoms. But the effects of the vaccine can still kick in in time to prevent serious illness.
Of course, if we are to beat this virus altogether, we will need vaccines that prevent infection and transmission. It’s not yet clear if current vaccines will prevent people who have been vaccinated from transmitting the virus, even for the original variants of the virus. Phase 3 trials have been unable to demonstrate this. But there’s good reason to hope they will – not least because of reports that the AstraZeneca vaccine appears to reduce infections by 67%.
Scientists who have been alarmed by the spread of diseases such as Sars, Mers and Ebola have been working for more than a decade on what they call “platforms” – systems that allow for the rapid design and creation of vaccines. In the past, developing vaccines followed a “one drug, one bug” approach, where scientists would scramble for a new treatment with each new virus. The traditional way of making a vaccine would involve growing a pathogen in bulk before injecting a small, neutralised amount of virus or bacterium into patients, whose immune systems would react to the antigens on its surface and develop antibodies that could ward off the disease.
But vaccine platforms allow scientists to identify a pathogen’s genes and then “plug” the genes for the part of the virus – the antigen – against which humans need to develop antibodies. Once you’ve developed a platform for delivering a vaccine, you can easily and quickly plug different genetic material into it, making it possible to develop vaccines for different variants much more quickly than before.
As new variants of Sars-CoV-2 – the virus that causes Covid-19 – are found, producing vaccines against them should be relatively straightforward. And so long as the UK’s Medicines and Healthcare Products Regulatory Agency treats these new vaccines like the annually updated seasonal flu vaccines, rather than as brand new vaccines, they should be available relatively quickly. In the future, we might even have a single injection every year to protect us against new variants of both Sars-CoV-2 and influenza.
Future vaccines against new variants will help reduce cases even further, suppressing transmission and eventually bringing the R number below one. At this point, the disease will start to die out. For now, however, even if the vaccines we have aren’t perfect against all variants, we need to go full steam ahead and vaccinate as many people as possible to prevent serious illness and deaths from Covid-19. Once we have reduced the number of hospitalisations and deaths, we can then focus on suppressing infection, transmission and mild-to-moderate cases of the disease.
Source: The Guardian
Keyword: The Oxford jab is less protective against the South African variant – but that’s no disaster | Vaccines and immunisation