By DONA MAGSINO, GMA News Published January 8, 2021 5:44pm Why is a second dose of COVID-19 shot needed? Health Undersecretary Maria Rosario Vergeire on Friday said it gives the user the benefit of having the maximum effect of the vaccine. "The second dose, just like any other vaccine, this provides you with your optimal efficacy kasi 'yung unang dose mo mayroon ka ng certain percentage na makukuha mo 'yung efficacy ng bakuna but that is already acceptable," Vergeire said in an online briefing. "That is an acceptable level pero pag binigyan ka ng second dose, it give you your optimal, 'yung maximum effect ng bakuna makukuha mo," she added.