Johnson: Vaccine cleared one hurdle, but 'several more to go'

"We absolutely cannot rely on this news, as a solution, and the biggest mistake we could make now is to slacken our resolve at a critical moment..." Johnson said.

Pfizer said more than 40,000 volunteers had been tested and the vaccine had proved 90 percent effective.

Johnson mentioned that the UK government had ordered 40 million doses, enough for a third of the population, as each person would need two doses.