On Wednesday, 6 April, the European Centre for Disease Prevention and Control (ECDC) and the European Medicines Agency (EMA) jointly published an initial position on a second Covid-19 booster dose with a messenger RNA ‘booster’.
The two European agencies do not see an urgent need to administer a fourth dose of vaccine to the general population. In fact, they believe that the data available at this stage are not sufficiently robust to demonstrate that the immunity to Covid-19 achieved through a first booster dose substantially declines in immunocompetent adults under the age of 79.
The available empirical data that the EMA and ECDC studied mainly come from Israel. The data reportedly indicate that a second dose administered 4 months after the first booster dose is likely to restore the antibody level obtained after the first booster, without raising any safety concerns. Immunogenicity data are available for a follow-up period of 3 weeks. Long-term data on the duration of this antibody level are reportedly not yet available, and only preliminary data exist on the effectiveness of this fourth dose against severe forms of Covid-19.
However, both agencies think that vaccinating adults over 80 years of age, who are more vulnerable, may be considered. The available data on vaccine safety and effectiveness only concern a fourth dose administered at an interval of 4 months after the third dose.
For severely immunocompromised people, a fourth dose is already recommended; the ECDC and EMA even suggest the use of monoclonal antibodies. Data are not yet available on whether further additional doses would benefit this population.
Both European agencies stress the importance of epidemiological and vaccine effectiveness monitoring. A change in the public health situation could, in their opinion, require a fourth dose of vaccine, including for the general population. Should this happen, vaccines more adapted to new variants of concern of the SARS-COV-2 virus would be preferred.
It should be noted that there are no data on a fourth dose of mRNA vaccine for people who received a primary vaccination series with a vaccine that uses a technology other than mRNA.
Link to the joint statement: https://aeur.eu/f/16d (Original version in French by Emilie Vanderhulst)