Published on July 26, 2021

Putting off second COVID-19 vaccine decreases efficacy against delta variant

While COVID-19 infections are on the rise again, a percentage of people have skipped their second vaccine, going against the recommendations for full effectiveness.

The Centers for Disease Control has authorized three COVID-19 vaccines from Johnson & Johnson, Moderna and Pfizer. While the Johnson & Johnson vaccine is administered in one shot, Moderna and Pfizer are completed in two doses. Dr. Christopher Penn, LMH Health infectious disease physician, said that for those who received Moderna or Pfizer, it’s vital to get both vaccines in the series.

“Studies have shown that getting only one dose of the mRNA vaccine results in a significant decrease in efficacy against the delta variant,” he said.

Simply put: Not getting the second vaccine increases your risk of being infected with COVID-19. While a single shot provides some protection, you’re more susceptible to contracting the virus without the second dose – including strains such as the delta variant.

“Getting both doses effectively doubles the beneficial effect and provides a stronger, longer-lasting immune response,” said Dr. Jennifer Schrimsher, LMH Health infectious disease physician.

According to Lawrence-Douglas County Public Health (LDCPH), 61% of Douglas County residents eligible have received their first dose of the COVID-19 vaccine. But only 54% of all eligible residents in the county have completed the series.

“Across all measured parameters – illness, symptoms, hospitalization and death – a partially vaccinated person is less likely to get the benefits a fully vaccinated person experiences,” she said.

I’m worried about side effects from the shot

Side effects of the shot may vary, depending on the type of COVID vaccine you receive. The Johns Hopkins School of Public Health shared that the most common side effect is soreness at the injection site. Other side effects include fatigue, headache, chills, muscle aches, joint pain and fever.

But if you’re putting off your second dose because of a reaction you had to the first shot, don’t fear. Dr. Schrimsher shared a few things you can do to reduce the side effects.

“It’s important to mentally prepare for any potential side effects,” she said. “Schedule your second dose when time will allow for you to rest. Take NSAIDs such as Advil or Aleve after the vaccine if side effects appear and use ice packs to treat any localized discomfort.”

When and where should I get my second dose?

The first and second doses of the vaccine must be completed by the same organization. If you receive your first dose at LMH Health, you should return to LMH to receive the second dose. Find a list of locations offering the COVID vaccine at

People who received the Pfizer vaccine should get a second dose at 21 days and those with Moderna at 28 days. While you should aim to get your second dose as close to that schedule as possible, Dr. Penn said it’s still important to make it a priority.

“Even if you’re outside the optimal window, get your second dose scheduled as soon as possible,” he said. “It’s not too late!” 

Autumn BishopStory by Autumn Bishop

Autumn is the marketing manager and content strategist at LMH Health.

Media Inquiries

For media inquiries related to LMH Health contact:
Amy Northrop
Director of Communication
Phone: 785-505-2931

Putting off second COVID-19 vaccine decreases efficacy against delta variant