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TThe news that the Oxford / AstraZeneca vaccine protects less against the South African variant of Covid-19 has caused much concern. But before we start to worry, we must first be clear about the details. While the current vaccine is less effective against the South African variant, it offers only slightly less protection when used in the variant first identified in Kent. And it is still believed that the vaccine is likely to protect against serious diseases caused by the South African variant.
This is an important detail. The current death toll in the UK is alarmingly high. Thousands of people are in hospital receiving treatment for Covid-19, and many more die at home. Our first priority is to alleviate the death toll and the number of hospital admissions, which overwhelm the NHS. If the Oxford / AstraZeneca vaccine is still effective in preventing serious diseases caused by the South African variant, it should help with both. A vaccine that prevents serious diseases is more than adequate for the moment to control the pandemic.
In general, vaccines of all types are most effective in preventing serious illness and least effective in preventing mild to moderate illness. Vaccines work by priming the body’s immune system so that if it finds the virus, it will recognize it immediately. After a person has been vaccinated, they may have enough neutralizing antibodies circulating in their bloodstream to destroy a virus before it can cause an infection. If they don’t, 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 by the virus. This immune response may take a while, in which the virus may begin to cause some symptoms. But the effects of the vaccine may still take effect in time to prevent serious illnesses.
Of course, if we want to defeat this virus completely, we will need vaccines that prevent infection and transmission. It is not yet clear whether current vaccines will prevent vaccinated people from transmitting the virus, even for the original variants of the virus. Phase 3 trials have not been able to demonstrate this. But there are good reasons to expect that they will, not least from reports that the AstraZeneca vaccine appears to reduce infections by 67%.
Scientists who have been alarmed by the spread of diseases like Sars, Mers, and Ebola have been working for more than a decade on what they call “platforms,” systems that enable rapid vaccine design and creation. In the past, vaccine development followed a “one drug, one mistake” approach, in which scientists struggled to find a new treatment for each new virus. The traditional way of making a vaccine would involve culturing a pathogen in bulk before injecting a small neutralized amount of virus or bacteria into patients, whose immune systems would react to antigens on their surface and develop antibodies that could protect themselves from disease.
But vaccine platforms allow scientists to identify the genes of a pathogen and then “plug in” genes for the part of the virus, the antigen, against which humans need to develop antibodies. Once you have developed a platform for delivering a vaccine, you can easily and quickly connect 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 found, producing vaccines against them should be relatively straightforward. And while the UK Medicines and Health Products Regulatory Agency treats these new vaccines as seasonal flu vaccines that are updated annually, rather than new vaccines, they should be available relatively quickly. In the future, we may even have a single injection each year to protect against new variants of both Sars-CoV-2 and influenza.
Future vaccines against new variants will help to further reduce cases, suppressing transmission and eventually reducing the R number below one. At this point, the disease will start to go away. However, for now, even if the vaccines we have are not perfect against all variants, we must go full blast and vaccinate as many people as possible to prevent serious illness and deaths from Covid-19. Once we have reduced the number of hospitalizations and deaths, we can focus on suppressing infection, transmission, and mild to moderate cases of the disease.
