Arguments have been made that because COVID-19 is such a serious disease that is rapidly spreading throughout the world and because vaccines can be made and delivered at a relatively slow rate, a first dose should be given and the second dose delayed until a large amount of the population receives the first dose. To be clear, it is known that the immune response to one dose of the vaccine is relatively weak, even though people who got their first dose had some protection against symptomatic COVID-19 infection. It is not known what will happen if people get only one dose.
It is possible that people who get only one dose will have only partial immunity to COVID-19 infection, resulting in higher risk that vaccine-resistant variants of SARS-CoV-2, the virus that causes COVID-19, will develop. There is also concern that people who get only one dose will think they have sufficient protection against COVID-19 infection and not get a second dose. There is no evidence that people who get only one dose have adequate long-term protection against COVID-19 infection.
The Centers for Disease Control and Prevention (CDC) recommends that the second dose of the COVID-19 vaccine be given within three weeks of the first dose for the Pfizer vaccine and within four weeks for the Moderna vaccine. No more than six weeks should lapse between doses, although if the second dose is not given during these time frames, it can be given without the need to repeat the first dose. It is not recommended to give the second dose any earlier than stated above, but if a person needs to get the second dose earlier, giving the second dose up to 4 days ahead of schedule is allowed.
Controversy for sure; at the end of the day, listen to the experts! This article was published in JAMA Network, a highly respected publication and is supported by the CDC.
Stay the course, stay well, mask up, get TWO vaccines, and stay tuned!