The group of experts advising the director general of that United Nations agency admits that, in case of great need, there should be an interval of 42 days between doses of the vaccine, but advises against giving just one dose to get more people vaccinated, especially in countries with a high rate of infections by the new coronavirus.

"In the current period, when the supply of vaccines is very limited, the preferential vaccination of international travellers would go against the principle of equity," the Strategic Advisory Group of Experts (SAGE) said.

"For this reason, and due to the lack of evidence that vaccination reduces the risk of transmission, the WHO does not recommend vaccination of travellers against Covid-19," they added, indicating that this recommendation will be revised as the supply of the vaccine increases.

The panel advised against giving the vaccine to pregnant women unless the benefits of vaccination outweigh the potential risks, in the case of people with other diseases or health workers at high risk of infection.

They also recommend that people with positive PCR tests postpone vaccination for six months.