Pfizer executives expressed measured optimism Tuesday over the prospect of providing a coronavirus vaccine in 2020 as the pharma giant reported lower third-quarter profits due to disruption in healthcare that dented drug demand.

Pfizer Chief Executive Albert Bourla said the drug giant could supply some 40 million doses in the United States in 2020 if clinical testing proceeds as expected and regulators approve a vaccine.

"If all goes well, we will be ready to distribute an initial number of doses," said Bourla, who pointed to a US government contract for Pfizer to supply 40 million doses by the end of this year and 100 million doses by March 2021.

But Bourla said the company still had not reached key benchmarks in assessing vaccine efficacy. Pfizer has said previously that it could have the data in October.

Bourla said the company expects to file for emergency use authorization for its Covid-19 vaccine in the third week of November, roughly in line with earlier timetables. 

Asked if he was "bullish" the vaccine would work, Bourla said: "I'm not bullish a vaccine will work. I'm cautiously optimistic that the vaccine will work." 

Regarding earnings, Pfizer reported a 71 percent drop in profit to $2.2 billion. The year-ago period included a large gain connected to a transaction.

Revenues dipped four percent to $12.1 billion, missing analyst estimates.

Pfizer estimated a revenue hit of $500 million connected to Covid-19 due to lower pharma demand in China and fewer wellness visits from patients in the US.

The company saw an 11 percent drop in its hospital business in emerging markets, primarily due to fewer elective surgeries in China and shorter in-patient hospital stays in the country.

This effect was partially offset by increased demand for the Prevnar-13 vaccine for pneumonia "resulting from greater vaccine awareness for respiratory illnesses," the company said. 

Pfizer also cited strong performance in its biopharma business due to good sales for cancer drug Ibrance, anticoagulant Eliquis and other medications.

Shares edged up 0.1 percent to $37.97 in afternoon trading.