The health decision was known a week ago and today it is a reality in almost all the provinces and the City of Buenos Aires. A third dose of the vaccine against the coronavirus people over 50 who have received Sinopharm and people over 3 years of age who are immunocompromised who have started the vaccination schedule with any component.
The decision was made based on recommendations from the WHO and international organizations: “The evidence shows that it is possible to advance in immunocompromised people, who have low defenses for any reason, older than 3 years who have received any vaccination scheme. We are going to work on planning and distribution with each of the provinces”, explained the Minister of Health, Carla Vizzotti. These two groups are made up of approximately 1.6 million people.
In addition, the official clarified that a third dose is not the same as a booster: “The third dose complements the primary scheme to extend protection and reinforcement, after having received the recommended primary scheme, what it does is to reinforce immunity periodically and that is at least 6 months after having received the primary scheme”.
In addition to reducing the effectiveness of vaccines, the third dose serves to raise the immune response in people with immunodeficiency or with immune changes naturally associated with aging (immunosenescence). It also serves to reduce the impact of mortality from COVID-19 in those over 50 and before the advance of the Delta variant in community transmission.
Following international recommendations and some clinical studies conducted in the country, the National Immunization Commission (Conain) advised the Ministry of Health of the Nation in the decision to add one more dose to the homologous or combined schemes in these two groups, following some stipulated parameters.
– Third doses for people over 50
“In those over 50, an additional heterologous dose will be prioritized, for which the use of a non-replicative virus vaccine is recommended [AstraZeneca, Sputnik V, and CanSino share that platform] according to availability, conditions that facilitate rapid decentralization and access, in order to cover the entire population with an expanded scheme in the shortest possible time,” indicates the document prepared by the Directorate of Control of Immunopreventable Diseases.
The official recommendation for that group is one dose of AstraZeneca. “The minimum interval of application of the additional dose will not be less than 4 weeks from the last dose of the primary scheme”, continues the recommendation.
– Immunocompromised vaccines
The decision to vaccinate immunocompromised people with a third dose was supported by several clinical studies carried out in the country that evaluated the protection afforded by vaccines against COVID-19 in transplant patients, who have been among priority groups in the access to immunization.
“People who require solid organ transplants are immunosuppressed before the transplant procedure. After transplantation, this condition is aggravated by pharmacological immunosuppression to prevent and treat graft rejection, and by the immune mechanisms that cause it. This situation is what makes them less responsive to vaccines, but their state of vulnerability marks the importance of being vaccinated. Therefore, in the transplanted the importance of additional dose is highlighted,” he told Dr. Daniela Hozbor, a researcher at the Institute of Biochemistry and Molecular Biology, under the Department of Biological Sciences, Faculty of Exact Sciences of the National University La Plata and Conicet.
“When analyzing these results on humoral response, it is suggested that transplant patients should be among the prioritized groups to receive the booster dose,” told doctor Mirna Biglione, a researcher at Conicet.
Thus, the third-dose vaccines authorized for those immunocompromised vary according to age. They will apply “to those who are undergoing cancer treatment for solid blood tumors, those transplanted under immunosuppressive treatment, people who in the last two years have received a hematopoietic stem cell transplant or who are immunosuppressed, patients with moderate or severe primary immunodeficiency, people with HIV and those who are being treated with high doses of corticosteroids or immunosuppressants”, read the ministerial recommendation.
Those over 18 who have already applied a complete scheme of Sputnik, AstraZeneca, and Sinopharm or the combination of Sputnik with AstraZeneca or a dose of an mRNA vaccine (Pfizer or Moderna), will receive a new dose of the first component of Sputnik V or a dose of AstraZeneca if they are between 18 and 39 years old or only AstraZeneca if they are over 40 years old.
In children between 3 and 11, it was indicated to complete the Sinopharm schedule with a third dose of the same brand, and in children between 12 and 17, the schedule of two doses of mRNA will be completed with another dose of the same brand. same platform. The interval for receiving the new dose is the same as for the other group. The indication for this third application is independent of the booster dose for the general population that can be announced as of December.
Is it safe to combine?
There are several studies worldwide that are being done on a combination of vaccines. Months ago, the results of the combination of the messenger RNA vaccine, produced by the companies Pfizer and BioNTech, with the vaccine developed by the University of Oxford with the company AstraZeneca, were published as a study still under peer review in The Lancet. This is the CombivacS study, which is carried out in Spain. A combined vaccination schedule using a second dose of the Pfizer / BioNTech vaccine (called Comirnaty) is being evaluated in people under the age of 60 who have received the first dose of AstraZeneca (Vaxzevria). They already have the first results of cellular immunity.
And a recent study presented to the CDC on Friday that tracked people who received combined boosters did not report any serious adverse events related to the vaccines. But experts also note that the data on combination vaccines is limited to a small number of people, especially compared to much larger studies that have shown each of the vaccines to be safe and effective on its own.
Allowing people to get any vaccine as a booster can be a boon for people anxious for an extra shot. “The future would be to combine vaccines for COVID-19 that are based on different platforms and even combinations of vaccines based on the same platform would be made,” Said Angela Gentile, a vaccine specialist at the Argentine Society of Pediatrics and the National Commission for Vaccine Safety. “If the coronavirus becomes an endemic like the flu every year, there is a possibility that different doses of vaccines will need to be combined. Today humanity needs both to combine vaccines and to have more doses in the context of a tragic and surprising pandemic,” he said.
Any booster shot, even if it’s the same as your first shot, will increase the number of antibodies that can fight the coronavirus. But in some cases, mixing vaccines may offer better protection, experts say. Early data has shown that following the first dose of Johnson & Johnson with an mRNA vaccine, Moderna or Pfizer, provided significantly higher levels of neutralizing antibodies.
Why are reinforcements effective?
Booster injections help train the body to fully respond to pathogens. A booster shot helps the body create memory cells that are long-lasting and capable of fighting pathogens for periods of time. It basically provides a second signal for the immune system to complete its response. They connect the immune system to respond to this pathogen, ”explained Costi Sifri, director of hospital epidemiology at the University of Virginia Health.
The infectologists agree that the application of a third dose is a valid health strategy in certain circumstances and in immunosuppressed patients, but they do not advise it today for the general population and they recommend reaching as many of the population as possible with two doses beforehand.