Coronavirus vaccinations are expected to begin soon in several countries, including Greece. As millions of people around the world will be vaccinated against COVID-19, the vaccine will be administered in two doses. COVID-19, scientists will monitor developments.
According to Nature, there are six key questions that scientists want answers to:
Based on clinical trials conducted to date on the three most advanced Western vaccines (Pfizer/BioNTech, Moderna, and Oxford/AstraZeneca), all prevent the onset of symptoms in the majority of those vaccinated (i.e., they protect against illness when the virus enters the body), but no vaccine can guarantee protection against infection (i.e., it does not guarantee that someone will not catch the virus). This leaves open the possibility that some of those who are vaccinated may remain vulnerable to infection without symptoms, and thus transmit the virus to others.
«The worst-case scenario is to have people walking around freely, but spreading the virus everywhere,» said virologist Stephen Griffin of the University of Leeds in the UK. Pharmaceutical companies plan to study precisely this issue in the future, namely whether their vaccines also protect against the infection itself. There are initial encouraging signs that vaccines can also reduce the frequency of asymptomatic infections—something that still needs to be confirmed in the future.
2. How long will the immunity provided by the vaccines last?;
There is no quick way to answer how long the antibodies created in response to vaccines will last, so it will take months or even years after the first vaccinations.
This will determine how often people will be reinfected with the coronavirus. It will be important for public health authorities to monitor immunity over time and know when it begins to wane. To do this, they will need, among other things, to frequently test the population for antibodies. Keep in mind that there is a wide variety in people's immune responses for various reasons, which is why vaccines do not ’work« equally well in all people.
3. How effective will vaccines be in the elderly and children?;
Clinical trials of vaccines to date have not included large numbers of groups such as the elderly, children, and pregnant women. It is therefore difficult at present to assess how well the vaccines will work in these and other specific population groups (e.g., obese individuals). The evidence so far is encouraging that they trigger sufficient immunity in people over 65, but there is no evidence for children and pregnant women (Moderna announced on December 2 that it will test its vaccine specifically on children). Statistical data from a large number of vaccinated individuals will therefore be needed before scientists can be sure that no population group is inadequately protected by the vaccines.
4. How much will the effectiveness of vaccines differ in practice?;
All three of the most advanced Western vaccines have achieved the basic minimum efficacy target of over 50% and all appear to be safe, based on clinical trials to date. Scientists want to see how well each one «works» in practice, considering that two (Pfizer/BioNTech and Moderna) is RNA vaccines, while the third (Oxford/AstraZeneca) is DNA vaccine. It is likely that some types of vaccines will be more effective in certain population groups or will be better at not only protecting people from becoming ill, but also reducing the likelihood of infection with the virus and thus further transmission. The different costs and practical requirements of each vaccine (transport, storage, etc.) will also need to be assessed. Some vaccines may be more suitable for poorer countries. Of course, in this first urgent stage, according to immunologist Danny Altman of Imperial College London London, «things are clear: everyone grabs whatever vaccine their government can buy...».
5. Will the coronavirus be able to evolve in such a way as to evade vaccine immunity?;
Some viruses, such as influenza, mutate, which is also true to a lesser extent of the SARS-CoV-2. Scientists hope that the new coronavirus will not evolve in a way that will render first-generation vaccines partially useless. However, they are concerned that mass global vaccinations may exert enormous evolutionary pressure on the coronavirus to mutate and develop a strain that will evade the antibodies produced by the vaccines.
«We have never seen a virus like this before, under such pressure. So we don't know how the coronavirus will react,» said virologist Dr. Griffin. For this reason, scientists will monitor its gradual mutations and, if necessary, change the composition of the vaccines, developing a new generation of Covid-19 vaccines.
6. What about the long-term safety of vaccines?;
Scientists will monitor those vaccinated for any side effects beyond those that occurred during clinical trials. However, experience with vaccines to date shows that serious side effects do not usually occur.
