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TThe news that the Oxford / AstraZeneca vaccine is less protective against the South African variant of Covid-19 has caused much concern. But before we start to worry, we first need to be clear about the details. Although the current vaccine is less effective against the South African variant, it offers only slightly less protection when used on the variant first identified in Kent. And it is still believed that the vaccine will protect against serious illnesses caused by the South African variant.
This is an important detail. The current death toll in the UK is appallingly high. Thousands of people are hospitalized and being treated for Covid-19, and many more are dying at home. Our first priority is to reduce the number of deaths and the number of hospitalizations, which plague the NHS. While the Oxford / AstraZeneca vaccine is still effective in preventing serious illnesses caused by the South African variant, it should help in both of these cases. A vaccine that prevents serious illness is more than enough at the moment to bring the pandemic under control.
In general, vaccines of all types are the most effective at preventing serious illness and least effective at preventing mild to moderate illness. Vaccines work by preparing the body’s immune system so that if it encounters the virus, it recognizes it immediately. Once a person has been vaccinated, they may have enough neutralizing antibodies circulating in their bloodstream to destroy a virus before it can cause infection. If not, they will have memory cells, which can quickly produce the necessary antibodies. Vaccination also prepares the immune system to produce other responses, such as T cells, which destroy cells infected with the virus. This immune response may take a little while, during which time the virus may start to cause some symptoms. But the effects of the vaccine can still come in time to prevent serious illness.
Of course, if we are to completely defeat this virus, we will need vaccines that prevent infection and transmission. It is not yet known whether current vaccines will prevent people who have been vaccinated from transmitting the virus, even for the original variants of the virus. Phase 3 trials could not demonstrate this. But there are good reasons to hope that they will – not least given 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 enable the design and production rapid vaccine creation. In the past, vaccine development followed a ‘one drug, one bug’ approach, where scientists scrambled for a new treatment with every new virus. The traditional way of making a vaccine would involve growing a pathogen in bulk before injecting a small, neutralized amount of virus or bacteria into patients, whose immune systems would react to antigens on its surface and develop antibodies that could ward off the disease. .
But vaccine platforms allow scientists to identify the genes of a pathogen, and then “plug in” the genes for the part of the virus – the antigen – against which humans must develop antibodies. Once you have developed a platform to deliver a vaccine, you can easily and quickly insert different genetic materials into it, making it possible to develop vaccines for different variants much faster than before.
As new variants of Sars-CoV-2 – the virus that causes Covid-19 – are discovered, the production of vaccines against them should be relatively straightforward. And as long as the UK Medicines and Health Products Regulatory Agency treats these new vaccines as the seasonal flu shots that are updated every year, rather than as new vaccines, they should be available relatively quickly. In the future, we might even have just one injection each year to protect against newer variants of Sars-CoV-2 and the flu.
Future vaccines against new variants will help reduce cases even further, suppressing transmission and ultimately lowering the R number below one. At this point, the disease will start to go away. For now, however, while the vaccines we have aren’t perfect against all variants, we need to go ahead and vaccinate as many people as possible to prevent serious illness and death from Covid-19. . Once we have reduced the number of hospitalizations and deaths, we can then focus on suppressing infections, transmission and mild to moderate cases of the disease.
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