Adults aged 18 years or above at baseline Be at least three but no more than 6 months (+/- 4 weeks) from the date of 3rd dose of BNT162b2 vaccine at the time of consent Have received three homologous doses as primary vaccination against SARS-CoV-2 with BNT162b2 vaccine (vaccination status should be documented). Written informed consent from the subject has been obtained.

Adults aged 18 years or above at baseline Be at least three but no more than 6 months (+/- 4 weeks) from the date of 3rd dose of BNT162b2 vaccine at the time of consent Have received three homologous doses as primary vaccination against SARS-CoV-2 with BNT162b2 vaccine (vaccination status should be documented). Written informed consent from the subject has been obtained.

-Adults aged 18 years or above at baseline -Be no more than 9 months (+/- 6 weeks) from the date of second dose of BNT162b2 vaccine at the time of consent -Have received two homologous doses as primary vaccination against SARS CoV-2 with BNT162b2 vaccine (vaccination status should be documented). -No contra-indication against any of the vaccine products in the trial. -Written informed consent from the subject has been obtained.

-Adults aged 18 years or above at baseline -Be no more than 9 months (+/- 6 weeks) from the date of second dose of BNT162b2 vaccine at the time of consent -Have received two homologous doses as primary vaccination against SARS CoV-2 with BNT162b2 vaccine (vaccination status should be documented). -No contra-indication against any of the vaccine products in the trial. -Written informed consent from the subject has been obtained.