Filenews 4 January 2021
As governments around the world race to vaccinate as many citizens as possible as quickly as possible, but approved vaccines at the moment do not seem to be enough, scientists have now faced pressing dilemmas and opened up the debate.
Does the second dose of the vaccine have to be deliberately delayed in order for more people to make the first dose? Should even half doses be given, from not administering any? Could the second dose be from a different vaccine company than the first?
Some experts believe, according to the New York Times, that since the first dose provides some protection against Covid-19, the strategy - in the absence of adequate vaccines - should be to make the first dose the largest possible number of people, even if it means delaying the second dose or even half the first dose.
Health authorities in Britain have already chosen to delay second doses of Oxford/Astra Zeneca and Pfizer/BioNTech vaccines in order to provide partial first-dose immunity to more people. On the contrary, the authorities in the US are vertically opposed to this idea. As chief infectious surgeon Dr. Anthony Fawch told CNN Friday, "I wouldn't support that. We're going to keep doing what we're doing." But on Sunday Monsef Slaoui, scientific head of the US national vaccination company "Warp Speed", said that - amid a limited supply of vaccines - two and a half doses (instead of two whole) of the Moderna vaccine are being considered to some citizens.
In the US, but also in other countries, particularly in Europe, there is frustration at the speed of vaccinations, as expectations for the number of vaccinated by the end of 2020 have been disproved. Countries such as Israel, which has managed to obtain large quantities of vaccines from the outset and already vaccinate more than 10% of its population, are an exception worldwide.
In the U.S. by Sunday about 4.2 million people in the U.S. had made the first dose of the vaccine, just over 1% of the population, against an initial target of 20 million by the end of 2020.
All vaccines to date (Pfizer/BioNTech, Moderna, Oxford/Astra Zeneca) require two doses. The first dose "teaches" the immune system to recognize the SARS-CoV-2 coronavirus, while the second "remembers" it in the long run. Clinical trials showed greater efficacy when the interval between the two doses was three to four weeks. Some protection is created after the first dose, but it is unclear how strong and lasting it is.
However, some scientists argue that the emphasis on administering the first dose to more people, at the cost of delaying the second dose, can save more lives than if half of people are vaccinated with both doses based on initial programming.
In the US the authorities keep vaccines available to make the second dose on time, but in Britain they prefer to postpone the second dose for later (up to 12 weeks, i.e. three times the time) in order to make more first doses.
Some American scientists fear that this delay tactic can be disastrous, partly for psychological reasons. "The longer the interval between doses, the more likely it is that people will forget to do the second dose. People may not remember what vaccine they did and we don't know what impact the combination of vaccines can have," said biologist Sveta Bansal of Georgetown University.
Dr Slaoui, who heads the vaccination operation in the US and does not rule out administering two-and-a-half doses, said that "the approach of some countries to delay the second dose can backfire and reduce confidence in vaccines."
What companies say
The pharmaceutical companies themselves have different positions. In the Oxford/Astra Zeneca clinical trial some volunteers in Britain took the two doses several months away, yet gained some protection against Covid-19. Greek-born executive vice president of the company Menelaos Pangalos said that a prolonged interval between doses "gives a lot of flexibility in the management of vaccines, depending on their available offer" and added that delaying the second dose "can help countries vaccinate large sections of their population to protect them quickly".
On the other hand, Pfizer's representative appeared more cautious, saying that "although partial protection from the vaccine appears to begin on the 12th day after the first dose, two doses are required to achieve maximum protection of 95%. There is no evidence to suggest that protection after the first dose is maintained after the 21st day."
A spokesman for Moderna said the company does not wish to comment at this stage on any changes to its dosing. Scientists generally believe that the second dose should not be far from the first, so that the booster dose is done while the body can still recognize the coronavirus thanks to the first dose. But it's unclear when this "window of opportunity" begins to close in the organization.
Distinguished Japanese-born professor Akiko Ivasaki of Yale University, who supports delaying the second dose, estimates that it can be administered even a few months after the first, which is the case with vaccines for other diseases, without a problem for their effectiveness. As he said, "let's vaccinate as many people as we can now against Covid-19 and give them the second dose when more vaccines are available."
Infectious scientist Dr. Robert Wachter of the University of California-San Francisco agrees with this strategy. But his fellow university infectious surgeon Phyllis Tien disagrees, arguing that delaying without tangible supporting evidence "is like going to the Wild West. We must follow the plan: 21 days between the two doses for Pfizer vaccine and 28 days for Moderna".
On the other hand, according to Slaoui, in Moderna clinical trials, people aged 18 to 55 who took two half doses of 50 micrograms (instead of the entire 100 micrograms) experienced a similar immune response. That's why the company and the U.S. Food and Drug Administration (FDA) are already considering approving two-and-a-half doses on a larger scale.
According to Slaoui, while there is insufficient evidence to support the delay of the second dose, there is evidence in favour of half the doses, at least for the Moderna vaccine. Other scientists, however, appeared sceptical. As vaccine expert John Moore of Cornell University in New York said, "cutting the dose in half is not something I'd like to see unless there's an absolute need."
Source: eyenews/KYPE
