Influential government advisers will debate Friday if there’s enough proof that a booster dose of Pfizer’s COVID-19 vaccine is safe and effective — the first step toward deciding which Americans need one and when. - AP Stream your PBS favorites with the PBS app: https://to.pbs.org/2Jb8twG Find more from PBS NewsHour at https://www.pbs.org/newshour Subscribe to our YouTube channel: https://bit.ly/2HfsCD6 Follow us: Facebook: http://www.pbs.org/newshour Twitter: / newshour Instagram: / newshour Subscribe: PBS NewsHour podcasts: https://www.pbs.org/newshour/podcasts Newsletters: https://www.pbs.org/newshour/subscribe