The French health authority Haute Autorite de Sante has recommended that only a single shot of COVID-19 vaccine should be given to people who have already been infected with COVID-19.
The HAS said in a statement that people previously infected retain an immune memory that calls for only a single dose.
"The single dose of vaccine will act as a reminder", the health authority added.
The statement, printed on the HAS website, said that people who have had a positive coronavirus test, or antibody test, should be considered protected for at least three months by "post-infectious immunity".
It added: "Current data do not allow to rule on the immune response beyond six months. The HAS therefore recommends that the vaccination be carried out within a period of almost six months and confirms that it should not be considered before a period of three months after infection."
It continued: "At this stage of knowledge, people who have already been infected retain an immune memory. This leads the HAS to offer only one dose to people who have been infected... regardless of how long the infection has been. The single dose of vaccine will thus act as a booster."
Two exceptions were given - people with proven immunosuppression - especially those receiving immunosuppressive therapy - "should, within three months of the onset of SARS-CoV-2 infection, be vaccinated by the two-dose schedule", it said.
And people who have received a first dose of vaccine and who develop coronavirus in the days following their first vaccination should not receive the second dose within the usual timeframe, but within three to six months after infection.
The decision is the first of its kind, with all other EU countries still following the guidelines of two shots per person.
All three COVID-19 vaccines approved for use in the European Union are administered in the form of two doses, delivered several weeks apart. Clinical trials have showed that immunity against the disease is significantly higher after individuals receives two doses.
France began its vaccine rollout in January and by Friday 2.1 million people in the country had received at least one vaccine dose, with almost 535,800 having already received two. However, the country faces a long-standing battle against vaccine-sceptics, with more than 40% of its population saying they would not be willing to accept immunisation if it was offered.
By Friday Britain had administered more than 13 million first doses of the vaccine, with a policy of giving booster jabs within 12 weeks to everyone.
Two recent US studies, reported in the British Medical Journal, suggested that a single vaccine dose may be enough for people who have already recovered from COVID-19.
One paper said that immunity in individuals who had had COVID and then received a single vaccine dose was "equal to or even exceeds" that of people who have not had COVID but received two vaccine doses.
In a paper published on Thursday regarding the Oxford/AstraZeneca vaccine, the World Health Organization said: "The recommended dosage is two doses given intramuscularly with an interval of eight to 12 weeks."
It added that "additional research is needed to understand longer-term potential protection after a single dose".
However, the implications of just administering one dose has been questioned by Eleanor Riley, professor of immunology and infectious disease at the University of Edinburgh, who said that in practice the process could be difficult to implement and keep track of.
“The authors of both papers suggest that people who have had a PCR confirmed COVID-19 infection may only require one dose of the vaccine," she said.
"Certainly, this would appear to provide them with protection that is at least as good as two doses of vaccine.
"However, incorporating this into a mass vaccination programme may be logistically complex and it may be safer, overall, to ensure that everyone gets two doses.”
Lawrence Young, virologist and professor of molecular oncology, at the University of Warwick, agreed thatthe approach may be viable if vaccine supply became an issue. However, he said more research was needed before considering changing advice on the number of doses people should receive.
He said: “If future work can confirm this high level of immunity post a single mRNA vaccine in this group of individuals, this could become a viable option when there are concerns around vaccine supply.”
A vaccine still in development by Johnson & Johnson works with a single dose, but it is yet to receive emergency use authorisation from regulators.
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