the biden administration is moving aggressively to fight against the surging delta variant by recommending booster shots in the fall and confronting republican governors fighting masking in schools and requiring nursing home staff to be vaccinated. all of this as the washington post reports criticism of the cdc for being too slow to share data about how the vaccine strength was waning against the delta variant. all questions today for the president's top medical adviser dr. anthony fauci director of infectious diseases, dr. fauci, thank you very much for being with us. it is an important day. >> it is. >> first, what drove the administration to recommend these booster shots starting september 20th?