Pfizer free or Sinovac pay.
Mixing two different vaccines can produce better immunity than using just one because the immune cells become familiar with slightly different versions of the threat, and can therefore recognize it even better.
Pfizer Pfizer can be given as a follow-up to a homologous dose of 1 dose at least 6 months after the Pfizer primary vaccination.
If this was known then, why did the government even buy these vaccines? Now : Pfizer Booster Dose For Sinovac Vaccine Recipients Too! We do not vet all comments and cannot vouch for their content.
China-based Sinovac's vaccine uses an inactivated version of a coronavirus strain that was isolated from a patient in China.