(New York, NY)  --  Pfizer says trials suggest its coronavirus vaccine is effective against a variant that first emerged in South Africa.  Pfizer also says a new company study shows its vaccine was more than 90-percent effective six months after volunteers got their second dose.  The drugmaker says this new data likely is sufficient for the vaccine to meet FDA criteria for full approval.  Pfizer's vaccine along with those from Moderna and Johnson and Johnson are being distributed under Emergency Use Authorizations.