Vaccine: not ideal, but delaying the second dose also offers protection

The national government reported on Monday that it was evaluating the postponement of the application of the second dose of the Russian vaccine Sputnik V against the coronavirus. The goal is to ensure that more people receive at least the first injection, to achieve partial immunity to the virus.

“In this context of a pandemic, it makes a lot of sense to think that more people can be vaccinated with the first dose and postpone the second until the epidemic is already under control,” said the Secretary of Access. to Health, Carla Vizzotti.

In other countries, they are also exploring more flexible vaccine strategies so that they can immunize more people in the short term and mitigate the effects of the second wave, which is hitting hard in the United States and Europe.

The vaccines from Pfizer, Moderna and AstraZeneca are applied in these countries. For example, the UK allowed the application of the AstraZeneca formula with two doses, but with an interval of up to 12 weeks, instead of four, as has been proven.

Can you think of a similar strategy for Argentina with the Sputnik V vaccine?

Belkys Maletto, expert in vaccines and immunology from Conicet and the National University of Córdoba (UNC), ensures that all authorized vaccines have been tested with two doses and should be used that way. “But in a period of a pandemic, alternative routes are sometimes sought,” he explains.

Vaccines stimulate the immune system to generate antibodies and a longer lasting response (cellular immunity).

On this point, Maletto explains that the phase 1 and 2 trials that began in March could give an idea of ​​this response from memory, although he specifies that these tests do not measure effectiveness, like phase 3.

For his part, Gabriel Morón, another vaccine expert from Conicet and UNC, was surprised by the idea. “It seems to me that the decision has more to do with production than a health strategy. It would be nice if they clarified it, ”he said.

Immunity is not efficiency

Phase 1 and phase 2 trials of the Sputnik V vaccine show that the first dose already produces immunity. One hundred percent of the volunteers developed antibodies with the first dose, says Maletto.

“Regarding cellular immunity (memory), the percentage drops to 77.8% for CD4 and CD8 T cells. With the second dose, the percentage is higher, ”explains the researcher.

Morón understands that these studies have shown antibody levels that are not optimal (as with two doses) and it is not known how long the cellular response lasts.

Further, he insists that measuring immunity does not measure effectiveness. “No vaccine study has determined what is the minimum level of antibodies that a person must develop to be protected,” he explains.

And he adds: “Researchers are taking samples from those vaccinated, both those who were protected and those who were not, to compare their antibody levels.”

Meanwhile, Maletto suggests: “The strategy may be not to give a single dose, but to space the time between the 1st and 2nd, so as to cover more people with what is available and then perform the second injection. “

The national government assured that the second injection of Sputnik V could be applied up to 60 days after the first.

“The second dose is necessary to consolidate the immune response, to homogenize the response in the whole of the vaccinated population and perhaps also to consolidate the immune response from memory”, concludes Maletto.

Alexander Gintsburg, director of the Gamaleya center that developed Sputnik V, said that after the first dose, protection takes three weeks and lasts about three to four months.

Based on these data, the Russian government yesterday approved a phase 2 clinical trial (150 volunteers, double-blind with placebo) to analyze a light version of the vaccine with only the first component. They estimate that the efficiency is 85%, as Russian President Vladimir Putin said a few days ago.

The big difference: Sputnik V uses two formulas

An important difference between Sputnik V vaccine and others is that each dose of the Russian formula is different. In the others, the same thing is repeated.

Countries can then choose to use the batch that was intended for the second dose in other people and thereby expand the population that receives at least one injection.

This cannot be done with Sputnik V, as the second dose cannot be given as the first injection. Or at least it is not studied.

Morón explains that England have proposed a more flexible regimen because it has the advantage of using those of Pfizer or AstraZeneca, in two equal doses. “In Sputnik V, they are different. So if you buy 10 million vaccines (with two doses), you have to give them to 10 million people. You cannot apply a dose of 20 million ”, he illustrates.

Russia was struggling to manufacture this second dose of the vaccine on a large scale. The Sputnik V will be manufactured in India, South Korea and Brazil.

Last week, national government sources trusted a new plane that would depart these days to search for a batch of 300,000 vaccines of this second component. In turn, they slipped that another larger shipment could arrive at the end of the month, but that it would mostly consist of the first dose.

In total, there are already 16,768 Cordovans vaccinated

Yesterday, 2,407 people applied Sputnik V in the province. Most of them were women.