The Final Dose of COVID-19 Vaccines Could be More Important than the First

Most West Virginians who received the Moderna or Pfizer COVID-19 vaccines are planning to get both shots. However, for whatever reasons, many aren't going back for their second dose.  The Centers for Disease Control (CDC) says that "ensuring second dose completion of the vaccine is critical in helping to protect people from COVID-19."

Based on work with other vaccines, Epidemiologists have learned that booster shots help immunity to stick, and the same is expected from the Pfizer and Moderna vaccines. In the two-dose COVID-19 regimen, the first dose primes the immune system; the second dose ensures “that immunity really takes and is longer lasting,” explains Mark Rupp, chief of the Division of Infectious Diseases at the University of Nebraska Medical Center.

Angela Rasmussen, a virologist at VIDO-InterVac and Georgetown University's Center for Global Health Science and Security, likens the mRNA vaccines to a college course that teaches your body to recognize and fight off an infection. The first shot — think of it as “COVID 101” — introduces your immune system to the coronavirus, but the second shot “is like advanced topics in SARS-CoV-2,” she says.

"Your immune system is more likely to retain that knowledge for a longer period of time. And those immune responses, although we don't know for sure yet, are more likely to be durable or longer lasting,” she adds.

That extra dose makes it more likely that your body will win a fight against the coronavirus variants that are sparking concern. One of these variants, called B.1.1.7, first identified in the United Kingdom, is now the dominant strain of coronavirus circulating in the U.S.

Some mutations seen in the variants make it easier for the virus to infect the cells of the body, but the flood of antibodies that come after the second shot gives the body an extra boost of protection that can keep the virus from binding to the cells.

Emily Landon, an infectious diseases specialist and associate professor of medicine at the University of Chicago Medicine says that vaccines "train your body to fight off COVID, and if you have two training sessions, it's better than one training session. If you only get one dose of a two-dose vaccine, then when it comes to the variants, especially, you're fighting with one arm tied behind your back.”

Have you already missed your second shot? Experts say it's not too late to go back and get it — even if you're beyond the CDC's recommended six-week window. (Keep in mind, too, that some countries, including the U.K, have been administering the mRNA doses 12 weeks apart to stretch out their supply.)

Experts say that it would be better to get that booster dose, even if it's a little bit later, than forgoing it altogether.