The U.S. government is planning to launch phase 3 trials of three COVID-19 vaccine candidates, starting with Moderna’s as soon as next month, followed by AstraZeneca’s AZD1222 in August, and a Johnson & Johnson candidate in September.

John Mascola, director of the Vaccine Research Center of the National Institutes for Allergy and Infectious Diseases (NIAID), said the timelines are estimates and they depend on several factors, including FDA approval to proceed.

Moderna released details last week of a planned phase 3 trial of its COVID-19 vaccine candidate in collaboration with NIAID. The Massachusetts-based drugmaker said it has finalized the protocol for the trial based on FDA feedback and expects to begin dosing next month. The trial of mRNA-1273 is expected to enroll 30,000 participants in the U.S.

Moderna has also completed enrollment of the first cohort of healthy adults ages 18 to 54 in a phase 2 study of the vaccine, as well as a cohort of adults ages 55 years and older.

AstraZeneca received a contract from HHS last month that includes funding for a phase 3 trial with 30,000 participants and a separate pediatric trial. The company declined to comment on the timing.

J&J said yesterday that it plans to begin phase 1/2a trials of its vaccine Ad26.COV2-S next month. The company also said that it is in talks with NIAID “with the objective to start phase 3 trials ahead of schedule.”

Meanwhile, NIAID Director Anthony Fauci is putting together a COVID-19 Prevention Network (CoVPN) to help speed the development of vaccines. The collaboration is based on the HIV Vaccine Trials Network (HVTN), which Fauci founded in 1998.

Larry Corey, NIAID adviser and one of the network’s leaders, said the network is looking to evaluate between five and seven vaccines. The effort will involve the HVTN, the Fred Hutchinson Center, the HIV Prevention Trials Network and the PTN Infectious Diseases Clinical Research Consortium at Emory University.