Washington, Aug 23 : The US is expanding its manufacturing of Covid-19 vaccines to help countries with low access to the lifesaving shots, the nations' top infectious disease expert has said. "We are now working on greatly expanding the capacity to allow us to donate hundreds and hundreds of millions of doses to the low- and middle-income countries," Dr. Anthony Fauci, medical advisor to President Joe Biden, was quoted as saying to CNBC. The COVAX programme, the international vaccine-sharing initiative -- coordinated by Gavi, the Vaccine Alliance; the Coalition for Epidemic Preparedness Innovations and the World Health organization (WHO) -- aims to provide two billion doses worldwide by the end of 2021. The US has given more than 120 million doses to 80 countries and has donated $4 billion in resources to the COVAX, Fauci said. "We are doing both," Fauci said of distributing booster shots and helping other countries. "We're very sensitive to the needs of the developing world who need vaccine doses, but we believe we can do both." Meanwhile, the US is seeing a surge in Covid infections and deaths due to the Delta variant. It continues to be the worst-hit country with the world's highest number of cases and deaths at 3,77,08,064 and 6,28,499, respectively, according to the latest update by Johns Hopkins University on Monday morning. A continued acceleration of cases could be avoided in the US if more people get vaccinated, Fauci said. "There's a lot we can do about it," Fauci said, noting that 90 million people in the US are eligible for vaccines but still haven't taken the shots. "We want to vaccinate the unvaccinated to the highest extent that we possibly can," said Fauci, director of the National Institute for Allergies and Infectious Diseases. Fauci also noted that it's hard to predict when the current delta outbreak will peak, however, once infections slow down he doubts that Covid -- unlike the flu, which requires annual shots -- will need recurrent boosters to maintain high levels of protection. "I don't think that's going to be the case. I think this third shot will take us a long way," Fauci said. /IANS