By Manojna Maddipatla

(Reuters) - Merck & Co Inc on Tuesday said it expects to report results from early-stage studies of two potential COVID-19 vaccines before the end of the year and has advanced an experimental antiviral drug into late-stage testing.

Merck was late to join the race to develop a vaccine to protect against the virus, which is again surging in many parts of the world including the United States. Rivals Pfizer Inc, AstraZeneca Plc and Moderna Inc are already deep into late-stage testing.

The company began recruiting trial participants in September for an early-stage study of its COVID-19 vaccine candidate V591, which it acquired with the purchase of Austrian vaccine maker Themis Bioscience.

Initial data showing whether V591 triggers an immune response in trial participants is expected by the end of the year, Merck research chief Roger Perlmutter said on a conference call.

The drugmaker is also collaborating with research non-profit IAVI on a second candidate that uses the same technology as Merck's Ebola vaccine. It is several weeks behind the V591 program but on a similar development track, Perlmutter said.

Merck said it was building facilities to be able to manufacture many millions of doses of the two vaccines. Drugmakers have committed to large-scale manufacturing of their vaccines before gaining approval to speed their eventual availability.

In addition to the vaccines, Merck has begun two late-stage studies of an antiviral drug against COVID-19 being developed in partnership with Ridgeback Biotherapeutics. The company said it has secured resources to produce millions of doses of the drug before the end of 2020.

The U.S. drugmaker also reported a higher-than-expected quarterly profit and raised its full-year earnings forecast. Merck shares rose more than 1% to $79.68.

Merck now expects 2020 adjusted profit of $5.91 to $6.01 per share, up from its prior forecast of $5.63 to $5.78 per share.

Excluding items, the company earned $1.74 per share, beating analysts' average estimates by 30 cents, according to IBES data from Refinitiv.

(Reporting Manojna Maddipatla in Bengaluru; Editing by Shailesh Kuber and Bill Berkrot)