Depends on how you define "effective."
The first generation vaccines, while not guaranteed to prevent infection, are still effective enough to reduce the likelihood of severe illness and death from all COVID variants.
My physician in the U.S., who, BTW, is also a specialist in infectious diseases and virology, advised me to get another booster here in Thailand as it had been ~6 months since my last booster and I had no plans to travel to the U.S. until late spring or early summer this year.