COVID-19 vaccine study has bad news for people who skip second dose

Researchers with Northwestern University have published a new study evaluating the body's response to the COVID-19 vaccine, particularly in comparison to natural immunity and emerging variants. Among other things, the study sheds light on why choosing to skip a vaccine dose or waiting for natural immunity can backfire spectacularly.

Some people are operating under the mistaken belief that it is ideal to contract COVID-19 and develop natural immunity to the disease. Aside from the obvious problem that this would require getting sick and taking the massive risk associated with COVID-19, the resulting natural protection may be far less robust than hoped.

According to the new study, catching the SARS-CoV-2 virus doesn't automatically guarantee the patient a high level of protective antibodies. As well, the researchers warn that people who previously had the disease won't necessarily experience a "robust" response to the first vaccine dose, underscoring the need to get the second dose.

The researchers say that developing and recovering from COVID-19 doesn't guarantee that you'll be immune from a second infection. The data is based on blood samples from people who had caught SARS-CoV-2 and who had received the Moderna or Pfizer COVID-19 vaccine.

Testing was conducted two months after the second vaccine dose was administered, revealing a decrease of 20-percent in antibody levels. When it came to people who'd had confirmed COVID-19 that was asymptomatic or mild, their two-dose antibody response was found to be around the same as in people who were fully vaccinated but hadn't been sick.

Thomas McDade, one of the researchers behind the study, also talked about the vaccine's protection against SARS-CoV-2 variants, saying:

As far as protection goes after vaccination, the story is the same for all the variants, including delta — the vaccine provides good protection, but not as good protection as the original version of the virus for which the vaccine was designed. Combine that with the fact that immunity wanes over time, you get increased vulnerability to breakthrough infection. So, it's two strikes right now — delta plus waning immunity among the first wave of the vaccinated