In the United Kingdom, authorities have reported that people should receive their second dose of the vaccine within 12 weeks of the first, and not within a few weeks as originally planned (Reuters)
Can I receive a second dose of the COVID-19 vaccine later than what is initially recommended? Can half of the doses be given? Using a different vaccine between the first and second doses, is it just as effective?
Governments around the world now face these questions in the face of an ongoing pandemic And after the emergence of different types of Corona virus, they appear to be more contagious.
Is that, With vaccine supplies limited and hundreds of millions of people waiting to get vaccinated against SARS-CoV-2, the situation leaves experts in conflict with Complex discussion On whether countries should vaccinate fewer people with the best protection possible or vaccinate twice as many people with a single dose, Covering a larger population but with slightly less protection.
The first country to suggest that twice as many people could be vaccinated with one dose and delay the second after 21 days initially recommended was the United Kingdom: The Advisory Committee advised health workers in England to reschedule appointments for the second dose after deciding to prioritize vaccinating as many people as possible with the first dose. .
As such, authorities have reported that people should receive their second dose of the vaccine (either from Oxford and AstraZeneca, or from Pfizer Bio-Tech) within 12 weeks of the first, not within a few weeks. Initially.
The goal is to get more people to receive an injection as soon as possible, even if the level of protection is below the level gained after receiving both doses.
Dr Chris Gill, an infectious disease specialist at Boston University, has argued that a single injection of Pfizer vaccine may be more effective than this estimate suggests. Looking at the data for a smaller window between when the first injection starts and before the second is started, Jill N. The Pfizer / BioNTech vaccine efficacy rate can reach 80-90% with a single dose.The goal is to get more people to receive an injection as soon as possible, even if the level of protection is below the level gained after receiving both doses (Efe).
Meanwhile, Moderna collected data from people who received only one dose of their vaccine. About 2,000 participants in the Moderna Phase 3 clinical trial received a single injection of a placebo or vaccine. In this population, the efficacy of a single dose of vaccine was about 80-90%.
The World Health Organization (WHO) supported the British position, and estimated that the second injection could be delayed for a few weeks “in exceptional circumstances for epidemiological contexts and supply restrictions.”
In the event that the vaccine used for the first dose is not available for the second dose, the British authorities have also authorized the administration of a different vaccine.
On the other hand, the United States took a wiser stance: FDA Director Stephen Hahn said these were “reasonable questions to consider and assess”, but that for making such a decision was “premature” and “not strongly supported by evidence.” Available. “
The debate exposed divisions among the experts, with prominent scholars putting themselves opposite each other.
Ideally, public policy should adhere to what has been demonstrated in clinical trialsBut the truth is, with a pandemic threatening – once again – to spin out of control, the situation for some is far from ideal.
“We didn’t choose three weeks for a Pfizer vaccine or four weeks for Modena because we thought it was perfect,” said Howard Furman, a public health expert at Yale University. This was the best estimate of the optimal time to administer the booster dose to boost immunity.
“So, slight changes in what we have already recommended can make a difference to get better use of our vaccines.”He told the agency France Press agency.
For him, delaying the second dose, which is essential for long-term protection, “should only be done with people under the age of 65 and without identifiable risks.”
What will happen in Argentina with the fifth SputnikA medical worker holds a bottle of the Russian Sputnik V Coronavirus vaccine in Serbia. File image. Vidja Grolovi – Reuters January 2021
Amidst the rising number of infections and easing health care measures by the population, Minister of Access to Health, Carla Vizotti, confirmed that the Argentine government is evaluating the application of a single dose of Sputnik V for the vaccination. Double the number of people in March.
“The most important health decision we have to take into account is whether we want to vaccinate 10 million people in March with two doses or if we prefer 20 million people with just one dose.”The national official said. He added: “In the context of the pandemic, it is very logical to think about the possibility of vaccinating more people with the first dose and delaying the second until the outbreak is brought under control.”
Previously consulted by InfobaeInfectious disease physician Roberto Dybagh (60,253 Minnesota) noted, “There is something going on in the world because of the problems laboratories face in volume production and they display three types of countries.” So, on the vice president of the Latin American Society of Pediatric Infection Medicine “There are the industrialized countries, which will get the doses they need, those countries with the lowest GDP that can benefit from some acts of solidarity, and a third group of intermediate countries, including Argentina, that will go to depend on the agreements that they were able to conclude.” .
For him, “On the other hand, slowing production and the difficulty of concluding agreements will lead to the start of discussion of the distribution issue with reduced production; if you have good implementation of good logistics and agreements, you can reach them and this will not happen in Argentina today.”
And after asking himself, “Could it be that with the vaccine shortage and the impending second wave, Latin America would not have to think of a first dose to try to contain it?” “In a country where there are no quick agreements or a guaranteed quantity of vaccines, I don’t know if I should not start exploring the possibility of trying to contain the epidemic situation with a single dose.
In this context, though There is no documentation of the efficacy of a dose of Sputnik V vaccine – At the moment, the only person available in Argentina was the President of Russia himself, Vladimir Putin, who in mid-December was surprised to expect it The Aesthetic Center was evaluating the development of another version of Sputnik V, which could be given in a single dose, but would have a lower level of protection.. The goal of this vaccine – which he called “mild” – is to provide the strong external demand he receives from various countries around the world.
“One of our options is to produce a so-called“ light ”vaccine from Aesthetic Center. This means that only one injection will be given that works for a shorter period of time and has a low level of protection, but is still 85% effective. Nevertheless, it can be applied to Tens of millions of people, “the Russian president said at his annual traditional press conference.Vladimir Putin expected the Aesthetic Center to evaluate the development of another version of the Sputnik V vaccine, which could be administered in a single dose, but would have a lower protection level (Efe).
The data was confirmed by Kirill Dmitriev, Director General of the Russian Direct Investment Fund (RDIF), which is financing the development of a vaccine for the Coronavirus in Russia. “The RDIF covers the expenses of the Aesthetic Institute to conduct the necessary tests because (the vaccine) is called Sputnik V-Light,” Sputnik news agency quoted Dmitriev as saying.
“This vaccine can be mainly directed to foreign markets where there are strong epidemic foci. We see a great demand for this vaccine and this approach by several foreign countries. ”He explained upon his consultation that Russia would choose the original version of Sputnik V, which is applied in two doses and provides greater protection for a longer period.
Only as a last resort
For Saad Omar, director of the Yale Institute of Health, the change in strategy is only justified in countries where supply is scarce.
In the United States, where 17 million doses have already been distributed to the states, the priority is to administer those doses that are already available.
As for injecting a different vaccine from one dose to another, for immunologist Akiko Iwasaki it could theoretically work, but Experts agree that it requires more research and should only be undertaken at present as a last resort.
One way to obtain more information could be to combine the results of several studies that have already been conducted to determine an effective antibody threshold for protection against COVID-19, according to estimates by Saad Omar and Nathalie Dean, a biostatistician at the University of Florida.
Then run smaller experiments to determine the vaccine dose that reaches this level.
One such study is underway to determine whether an injection of half doses of Moderna vaccine provides the same protection as full doses., According to John Mascula of the US National Institutes of Health (NIH), cited by him The New York Times.
But one fear haunts scientist Natalie Dean: These changes are helping to fuel public distrust of vaccines. According to her, any amendment, therefore, must follow the same licensing protocol used to approve urgent vaccines.
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