What data have been collected by vaccination experts in Britain. What the professor says about combining doses of different vaccines.
"The coronavirus variant that has appeared has changed the balance and shows us that there should be no complacency.. We have no time to lose ", says in a Facebook post Professor of Health Policy Elias Mosialos of the London School of Economics and Political Science (LSE), about what we know and what not from the vaccinations so far in Britain.
As he points out, "In Britain we are in a real road race with the coronavirus, after determining the rate of spread of the new - possibly more contagious- coronavirus variant. Despite the strict measures, Hospitals continue to be under pressure and tens of thousands of new infections are reported daily. Schools in London and other areas most affected by the virus, will remain closed for at least the next two weeks. At the same time, the vaccination committee updated the instructions, to vaccinate as many people as possible ".
Britain has approved two vaccines (of PfizerBioNTech and Oxford / AstraZeneca) and about one million people have already been vaccinated. According to the new instructions, every effort must be made, to complete the dosing for each with the same vaccine first used. But, if a second dose of a vaccine is not available, can be replaced with a vaccine dose from another company.
These new directives are at odds with those in the United States, where the American Centers for Disease Control and Prevention (CDC) state that the approved Covid-19 vaccines "are not interchangeable" and that "the safety and efficacy of the mixture have not been evaluated", concluding that everyone should receive two doses of the same vaccine.
Mosialos raises the question of whether British experts recommend mass vaccination even with a combination of doses. As he states, Both of these vaccines are safe and effective, while both target the coronavirus protein, so a second dose is possible, even with a different carrier, to enhance the immune response in the first dose. also, from cases of re-infection it is known that patients developed higher rates of antibodies to the second exposure to the virus. "Pandemic management is risk management. And to calculate the potential benefits and risks of such an approach, we need absolute transparency ", emphasizes Mr. Mosialos.
As announced in Britain, both vaccines will be given at intervals of four to 12 weeks and the priority is to give at least one dose of the vaccine, given the limited resources. This is because the first dose probably provides a significant degree of protection, while for the Oxford / AstraZeneca vaccine in particular the efficacy may be higher, when the interval between doses is longer.
It is recalled that the Oxford / AstraZeneca clinical trial was originally scheduled with a single dose, but a booster dose was added, when scientists realized that this would likely boost efficiency. Some volunteers received the second dose months after the start of the trial and the interval varied according to age group., while there was also the issue of different dosage.
Efficiency reported approx 60% for the group receiving two standard doses and approximately 90% for the group that initially received half and then the standard dose of the vaccine. What is less clear, is whether these differences are due to the lower first dose, in younger participants or in larger gaps between doses. The effectiveness of the vaccine between the ages 18-55 years old was 59% for the regimen with the two standard doses, against 90% for those who received half and then a standard dose. As reported by Mr.. Mosialos, whether this is due to the dosage or the time difference between the two doses, we do not know yet.
We can also not evaluate the approach recommended for the elderly 55 years, because there is no published data yet. There are, however, reports that unpublished data support longer intervals between doses. Most likely, the British regulator (MHRA) has evaluated all of these components before approving the current dosing protocol. "The arguments for the approach taken by (British) government, is the given urgent need. However, I consider it important that the unpublished data supporting the decision be announced. Not only for reasons of transparency but also to gain the trust of the people who will be vaccinated, which is the most basic point in the vaccination effort ", he emphasizes.
He adds that "the issue that has arisen in the United Kingdom, may arise in other countries. At the moment it is almost vaccinated 2% of (British) citizens, giving priority to the vulnerable. Currently, we have a specific ability to produce and sell vaccines and this may be enhanced. But, we can not predict the changes in the virus and whether they will cause changes in its transmission to the community ".