Monkey pox: why was the second dose of the vaccine postponed?

It is a decision that raises questions among some specialists and in the associative world.

Monkey pox: why was the second dose of the vaccine postponed?

It is a decision that raises questions among some specialists and in the associative world. The time between the two doses of vaccination against monkeypox, previously 28 days, has been extended for non-immunocompromised people, the Ministry of Health said Thursday, August 4. The ministry has indeed declared to AFP to have "recommended to the vaccination sites, in accordance with the opinion of the High Authority for Health (HAS) of July 7, to lengthen the spacing between the first and the second dose for non-immunocompromised people. However, no details have been given on the maximum time allowed by the authorities to obtain complete protection against the disease.

Two doses of vaccine are recommended for most eligible people. For those vaccinated against smallpox in the past, one dose is enough. For the immunocompromised, a third is recommended. So far, some 18,500 people have received a first dose of the vaccine in France.

There have been reports in recent days of cancellations of appointments for a second dose of the Monkeypox vaccine. "Many people have had their appointments for their second dose canceled, without any explanation. This is not acceptable and appointments must be honored," the AIDES association said on Twitter.

The Ministry of Health for its part underlined that "the second dose appointments already scheduled must not be canceled" and that "patients whose second dose would be evaluated as a priority by a doctor for health, treatment or exposure, will benefit from an appointment". On the other hand, "unscheduled second dose appointments can be scheduled later".

Why did the authorities decide to lengthen the spacing between the two doses? The objective is to vaccinate with at least one dose as many people as possible in the eligible population: men who have sex with men (MSM), trans people with multiple sexual partners, sex workers and professionals. health. This extension was motivated "due to a strong increase in vaccination on national territory since the launch of the preventive vaccination campaign on July 11, in order to guarantee the greatest number of people at risk access to vaccination as soon as possible over this summer period and thus ensure better collective protection”, wrote the Ministry of Health.

The HAS had recommended, in its opinion issued on July 7, a vaccination schedule “of two doses, spaced 28 days apart” but indicated “that a spacing of doses of several weeks could be considered in the event of a tension in the supply of vaccines ". Asked whether the extension of the deadline was linked to such tension, the ministry reaffirmed to AFP that "there is no tension in the supply of vaccines".

The Minister of Health François Braun repeated on Wednesday August 3, during his first visit to a vaccination center against monkeypox, that France had "enough to vaccinate the target population (...) namely 250,000 people ". After recalling the destocking of 42,000 doses, he assured that the government is "able to increase vaccinations according to needs". Faced with criticism of the slowness of vaccination, François Braun assured at the end of July that France had "not fallen behind" and affirmed that the stock of smallpox vaccines was "very substantial". However, he refused to specify the extent, pleading the "secret-defense" because smallpox can be used as a biological weapon.

At this time, the exact protection conferred by a single dose of vaccine is not known. As Le Monde recalls, the studies available, and in particular a phase 2 trial conducted between 2017 and 2019 with 1,600 volunteers in the Democratic Republic of the Congo, show a peak in the production of neutralizing antibodies two weeks after the second dose. A study conducted on macaques in 2008 suggests that a single dose protects against severe forms of the disease, but not against infection.

For Jean-Daniel Lelièvre, specialist in the Modified Ankara Vaccine (MVA) vaccine, "if the disease does not spread outside the MSM community, a one-dose vaccination may be relevant, as it offers individual protection. But the risk , by doing so, is not to block the chain of transmission and allow the infection of other people; we do not thus achieve the objective of collective protection", warns the head of the immunology department to Le Monde. clinic and infectious diseases of the Henri-Mondor hospital in Créteil (AP-HP). "Whatever the effectiveness of the vaccine after one or two doses, it will never be 100%," warned the Ministry of Health on Thursday, insisting on prevention in parallel.

In addition, as mentioned by Le Parisien, who consulted a document sent by Public Health France to hospital pharmacists, initially expired vaccines are used in order to avoid being out of stock. Thus, while a batch of Imvanex vaccines, from the Bavarian Nordic laboratory, initially expired on March 31, 2017, its expiry date was delayed to March 31, 2024 following "checks carried out by the National Security Agency of medication". The Directorate General of Health assures that "the activity of the vaccine did not vary between 2018 and 2022".

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