Short term, relative effectiveness of four doses versus three doses of BNT162b2 vaccine in people aged 60 years and older in Israel: retrospective, test negative, case-control study.

Short term, relative effectiveness of four doses versus three doses of BNT162b2 vaccine in people aged 60 years and older in Israel: retrospective, test negative, case-control study – The BMJ

Related recommendations:

Covid-19: Second boosters may benefit at-risk groups but have “minimal” impact for others, says WHO – The BMJ

COVID-19: Joint statement from ECDC and EMA on the administration of a fourth dose of mRNA vaccines –
European Centre for Disease Prevention and Control

Coronavirus (COVID-19) Update: FDA Authorizes Second Booster Dose of Two COVID-19 Vaccines for Older and Immunocompromised Individuals – U.S. Food & Drug Administration