Pharmaceutical titan Pfizer said that there are “no data” to show that a single dose of its covid vaccine offers protection from infection beyond 21 days, a media report said.

Pfizer: Single Dose of Vaccine Doesn’t Protect Beyond 21 DaysPfizer told Axios that some protection seems to begin as early as 12 days after the first dose.

But the New York health-care giant also said that two doses of the vaccine, separated by three weeks, represent the only treatment demonstrated to be 95% effective in Phase 3 trials, Axios reports.

It said that’s important because the U.K. National Health Service announced a change in its vaccine approach “to give as many people in at-risk groups their first dose, rather than providing the required two doses in as short a time as possible.”

The NHS said, “Everyone will still receive their second dose, and this will be within 12 weeks of their first. The second dose completes the course and is important for longer term protection.”

Pfizer shares recently traded at $36.44, down 0.8%. They have slipped 1.8% this year, as investors don’t see its finances benefiting much from the vaccine.

Morningstar analyst Damien Conover views the stock as a bit undervalued, putting fair value at $40.

“We believe the vaccine’s incredible speed to market reinforces [the] innovative power behind Pfizer’s wide moat,” he wrote this month.

But “we expect strong vaccine competition from” other companies, “which will likely significantly stem the pandemic, but also reduce the profitability of the covid-19 vaccine market,” Conover said.

“We expect the pricing power of the vaccines to be low with so many potential competitors.”