In-Depth: What to do if you miss the 42-day window for the second COVID vaccine shot Postponements, cancellations lead to worry Closures at the Petco Park Vaccine Super Station have led some San Diegans to miss their 42-day window to get the second COVID-19 shot. and last updated 2021-03-05 09:54:12-05 SAN DIEGO (KGTV) - Three separate closures at the Petco Park Vaccine Super Station have affected thousands of San Diegans waiting to get their COVID-19 vaccine. For some of them, it meant they missed the 42-day window the CDC recommends for the second shot. "It's very frustrating, and I don't know where to go," says Jeanne Monteleone, who has had her appointment for a second shot postponed three times.