Filenews 31 March 2021 - by Marilena Panagi
And the third dose of coronavirus vaccines may be needed, especially for older people in the autumn, at a time when the duration of action of available vaccines is the biggest unanswered question for scientists internationally.
"The biggest unanswered question, so far, is the duration of the vaccines' action," Associate Professor of Pharmacy, Christos Petrou, told "F", adding, however, that "the time is approaching when we will have some answers." But the UK, Mr. Petrou said, "has announced that it will proceed with a third, supportive dose to people over the age of 70 after September," expecting that by then it will be possible to administer vaccines "that will be able to cope with a greater range of mutations that some of the vaccines currently available cannot cope with."
Serious indications, which in fact 'no longer seem to be in doubt, exist and result from vaccination of more than 450 million people internationally in terms of the effectiveness of all available vaccines'. Now, Mr. Petrou said, "we have the ability to see and assess efficacy and safety in real-world conditions of use" and at the same time, "a significant number of studies show that the first dose of both AstraZeneca's "Vaxzevria" vaccine and Pfizer/BionTech's "Comirnaty" offer excellent prophylaxis at older ages, while the first dose of these vaccines was associated with a significantly reduced risk of SARS-CoV-2 infection in elderly residents in the UK."
Furthermore, "a study in Israel involving 600,000 people who had been vaccinated and 600,000 others who had not been vaccinated estimated that the effectiveness of vaccines in preventing death from Covid-19 was 72% for days 14 to 20 after the first dose, while the symptomatic disease was reduced by 57%, the hospitalization by 74% and the serious illness by 62% ". Seven days after the second dose, "there was a 94% reduction in cosymatic disease, 87% in the need for hospital admission, 92% in severe disease. There were only 9 deaths from Covid-19 in a population of 600,000 vaccinated."
These results, Mr. Petrou stressed, "demonstrate that the high expectations we have had of vaccines to a huge extent are being verified."
As far as safety is concerned, "no issues have arisen that disrupt the benefit-risk relationship, and this is what periodic safety data shows, as assessed every month."
In relation to 'rare cases of thrombosis accompanied by thrombocytopenia (reduced platelet count), the European Medicines Agency (EMA) has convened a special committee to examine them with a view to identifying whether they can actually be associated with vaccines'. However, as already announced by the EMA, 'this risk concerns all vaccines for coronavirus'. In Canada, however, "a specific recommendation has been introduced to treat such rare cases with Canadians identifying them as a possible vaccine-induced prothrombotic autoimmune thrombocytopenia". The mechanism that causes these incidents is under consideration. The frequency of these incidents may be 1 to 8 incidents per 1,000,000 ".
As regards the reduction of communicability after vaccination, 'more and more evidence from the use of the vaccine shows that it is decreasing, to a fairly large extent'. From the international data so far, as they emerge from the United States of America "where millions of vaccinations have already been carried out with Pfizer/BioNTech and Moderna vaccines, it is found that from the first dose, the risk of infection is reduced by up to 80% while when we go to the second dose the risk is reduced by 90%, which significantly reduces the chances of transmission".
There is a risk of re-infection
The infection by the coronavirus, "clearly causes the development of antibodies, however the risk of re-infection remains. Both in Cyprus and internationally re-infections are recorded and the risk found in older people is greater than in younger people. In particular, protection after infection in the elderly is recorded up to 3 months later and in younger people up to five or seven months'.
These data, Mr. Peter stressed, "in themselves tell us that every person, whether they have passed through the coronavirus or not, once they have the opportunity to be vaccinated, should be vaccinated and there is no recommendation on when to vaccinate a person who is already infected with the coronavirus. Since there is a risk of re-infection, vaccination protects in any case. Furthermore, it has been observed that people who had become sick and subsequently received the first dose of the vaccine showed significant reinforcement in their body's defences'.
