Would it be possible, given the increase in COVID-19 cases around the world, to postpone the second dose of vaccines and try to give less immunity to more people? And use different vaccines between the first and second doses? Or give half a dose of any of the approved formulations to inoculate twice as many people with the remainder?
All these questions have been analyzed by science since SARS-CoV-2 mutations and the speed at which infections are increasing seem to be winning the race to immunize the population.
It is that since the vaccines of Pfizer and BioNTech, Moderna, AstraZeneca and Sputnik V were approved in different countries, to the difficulties of the laboratories to meet the demand for supplies was added the discovery of new strains of the virus that has been the world in suspense for more than a year.
The first country to raise the possibility of inoculating twice as many people with one dose and delaying the second beyond the initially recommended 21 days was the United Kingdom: the advisory committee advised health workers in England to reschedule appointments for the second dose after it has been decided that vaccinating as many people as possible with a first dose should be the priority.
So things, UK authorities reported that people should receive their second dose of vaccine (either from Oxford and AstraZeneca or from Pfizer BioNTech) within 12 weeks of the first, rather than within a few weeks as initially planned.
Is that experts know that while vaccines are intended to give a person the second dose between 21 and 28 days after the first, there is a three-month window period within which a person can complete their immunization. And on that argument they base these desperate attempts that aim to get more people to receive an injection as soon as possible, even if the level of protection is lower than that acquired after receiving both doses.
Dr. Chris Gill, an infectious disease specialist at Boston University, said that a single injection of Pfizer’s vaccine may be even more effective than this estimate suggests. Looking at the data for a smaller window between when the first injection should have started working and before the second was triggered, Gill said that the Pfizer / BioNTech vaccine can have an efficacy rate as high as 80% or 90% with a single dose.
Moderna, meanwhile, collected data from people who only received one dose of their vaccine. About 2,000 participants in Moderna’s Phase III clinical trial received a single injection of a placebo or the vaccine. In that population, the efficacy of the single dose of vaccine was approximately 80% to 90%.
The World Health Organization (WHO) supported the British position, estimating that the second injection could be delayed for a few weeks “in exceptional circumstances of epidemiological contexts and supply limitations”.
And in the event that the vaccine used for the first dose is no longer available for the second, the British authorities also authorized the administration of a different vaccine.
The United States, by contrast, took a much more cautious line: The director of the drug agency (FDA), Stephen Hahn, said that these were “reasonable questions to consider and evaluate”, but that making such a decision was “premature” and “not solidly supported by the available evidence ”.
The debate exposed the divisions among the experts, as leading scientists positioned themselves in opposite places.
Ideally, public policies should stick to what was shown in clinical trials, but the truth is that with an epidemic that threatens – again – to get out of control, for some the situation is far from ideal.
So things, a document statement of the US Food and Drug Administration (FDA for its acronym in English) states that the agency closely follows “discussions and news reports on how to reduce the number of doses, extend the time between doses, change the dose (half dose) or mix and match vaccines to immunize more people against COVID-19”. “These are all reasonable questions to consider and evaluate in clinical trials. However, at this time, it is premature to suggest changes to the doses or schedules authorized by the FDA for these vaccines and is not strongly based on the available evidence, they said. Without appropriate data to support such changes in vaccine administration, we run a significant risk of putting public health at risk, undermining historic vaccination efforts to protect the population from COVID-19. “
Infobae In this regard, he consulted the infectious disease doctor Roberto Debbag (MN 60253) for whom “half of the scientific library talks about alternatives on how to ensure that a high number of people in the world have at least a first confrontation with the vaccine and they spoke out in favor of that; while the other half is against it, among them Anthony Fauci himself believes that people should receive both doses at the proper time ”.
And after considering that “This (people receiving both doses at the time the study was designed) is what should happen if there were enough doses”, Debbag analyzed that “There are currently two careers in the world: one is the one that is having the virus itself, modifying and generating mutational variants whose ultimate goal is to transform into another virus, which I hope does not happen, but the truth is that SARS-CoV-2 is gaining speed in the generation of new variables.
While the second race that -for him- is the one to be won “is to get the largest possible amount of the world’s population to acquire vaccinesTherefore, the more effective and safe vaccines, the greater the probability of access in different countries ”.
“As this second race is not happening in an equitable way, what happens is that three groups of countries were in evidence: the industrialized ones that did the research, develop the vaccines and will access more quickly; those with the lowest GDP – in the region we have Haiti, Nicaragua and Bolivia – that possibly benefit from free vaccines and finally there are all the others, where access to the vaccine will be more difficult ”, he analyzed.
Regarding the different strategies proposed to try to advance immunization at the rate that the virus does, Debbag said that “Regarding reducing the number of doses, it is already known that the next vaccines that are arriving are one-dose vaccines, which are still being investigated”, in reference to the developments of the Janssen and Cansino laboratories. “Now, in vaccines that are two doses, reducing the number of doses is not a valid alternative, what can be done is to quickly give a first dose and extend the time interval until the second so that the efficacy is really as the studies show, “he added.
“If we achieve a vaccine that in one dose has high efficacy, it would allow to improve logistical aspects, less quantity will be needed to supply the world and thirdly it would solve the problem of the patient returning for the second dose, something that is already seen as one of the greatest challenges in the fight against COVID-19 ”. For the infectious disease doctor Eduardo López (MN 37586), however, “there is no concrete data that a significant protection is achieved with a dose; Phase III studies that demonstrate the efficacy of single-dose vaccines are lacking ”.
“Changing to half a dose is possible, because for example the Pfizer and Moderna vaccines are very similar in their research structure, production and also in their efficacy and safety data, with the exception that Pfizer’s has 40 micrograms and Moderna’s, 100 – he continued analyzing -. So the FDA is possibly evaluating giving half the dose of Moderna’s vaccine to make it comparable with Pfizer, but we also have to do immunogenicity studies with that ‘reduced’ vaccine specifically of which there are already some in Phase I “.
About the alternative mix and match (mix different vaccines), Debbag pointed out that “Today it cannot be done, but there is a light that these combinations will be investigated in the same scheme: for example, AstraZeneca with a second dose of Sputnik V, or AstraZeneca with some other vaccine and so on; that is the future but without any doubt it will have to be studied in research phases ”.
For Saad Omer, director of the Yale Institute of Health, a change in strategy is justified only in countries where supply is scarce.
In the United States, where 17 million doses have already been distributed to states, the priority is to administer these doses already available.
As for injecting a different vaccine between one dose and another, for the immunologist Akiko Iwasaki it could work in theory, but experts agree that it requires more research and should not be done at this time except as a last resort.
The strategies are as diverse as the forms that the enemy seems to be able to take to fight. The challenge is to achieve the long-awaited herd immunity, something that at the moment no plan seems to be close to achieving.