Press release no. 670 - In its meeting of 2 and 3 November 2021, AIFA’s Technical Scientific Commission (CTS) expressed its views on the Ministry of Health request concerning the possibility to administer a booster dose to subjects who have received a single dose of Janssen vaccine, and the related timeline.

Given that COVID-19 vaccine Janssen is the only COVID-19 vaccine authorised with a single-dose schedule and that, in immunization, a booster dose can be considered a well-established strategy for most vaccines, the opportunity to provide a booster dose appears to be supported by a solid rationale.

Based on an in-depth investigation carried out by Agency’s experts, the CTS found that data available indicate a substantial stability of the immune response, both humoral and cellular, up to 8 months after the administration of a dose of Janssen. Protection against severe disease, hospitalisation or death is also substantially stable until at least 6 months after vaccination. At the same time, however, a slow decline in vaccination effectiveness against the mild/moderate form of the disease is observed over the months.

The latest evidence confirms the effectiveness of a dose booster (especially with an mRNA vaccine) in enhancing the immune response to COVID-19 vaccine Janssen.

For this reason, subjects who have received COVID-19 vaccine Janssen should be administered a heterologous booster dose with an mRNA vaccine (in authorised dosage for the booster dose) from 6 months after the first dose.