u/Icy_Application_3420

My adult cats received 1 dose of a FeLV vaccine at the end of Feb. I wasn't made aware that they need 2 doses for an initial series (they hadn't been vaccinated before). For optimal effectiveness do I need to restart the series and give 2 vaccines 3 weeks apart? Or is it like some human vaccines where the second dose needs to be given at least X weeks later but it's not a problem to give later than that?