The drug trial has been paused for safety concerns.
The China Daily began referring to Shulan as "the last pandemic hotspot in the country."
President Donald Trump said on Tuesday the World Health Organization had to improve how it treated the United States and other countries or Washington would pull out.
Earlier, Trump said the WHO had "done a very sad job" in its handling of the virus and he would make a decision soon on US funding.
US President Donald Trump has fiercely questioned the WHO's performance during the pandemic and led international criticism of China's handling of the early stages of the crisis.
The Trump administration will "agree to pay up to what China pays in assessed contributions" to the WHO, Fox News reported, quoting from the letter.
The World Health Organization has also stopped supporting eastern Syria, an area of millions of people who are recovering from ISIS atrocities.
More than 100 potential vaccines are being developed, including several in clinical trials, but experts have underscored the difficulties of finding vaccines that are effective against coronaviruses.
The WHO said in April a vaccine would take at least 12 months.
An average of 192,000 weekly coronavirus-related attacks have been identified during the past three weeks, representing a 30% increase compared to previous weeks, researchers said.