Pfizer: “No data” to show the single dose of vaccine provides protection after 21 days

Pfizer said in a statement that there was “no data” to show that a single dose of coronavirus vaccine would provide protection against infection after 21 days.

Why it matters: The UK announced on Wednesday that it would shift its vaccination strategy ‘to give as many people in the risk groups their first dose, rather than giving the required two doses in a short time.’ Some provinces in Canada do the same.

  • Pfizer confirmed in response that although some protection appears to have started as early as 12 days after the first dose, two doses of the vaccine – separated by three weeks – are the only treatment that was 95% effective in Phase 3 trials.
  • “Everyone will still receive their second dose and it will be within twelve weeks after their first dose,” the British government added in a statement. “The second dose completes the course and is important for long-term protection.”

The whole picture: Pfizer’s warning comes as many countries, including the US, are debating how to deploy the vaccines quickly in the most efficient way possible. The US is set to be well below the target of vaccinating 20 million people by the end of 2020, with only 3 million single doses administered on Wednesday night.