Is It Safe to Get One COVID-19 Vaccine Now and Another Later?

The Johnson & Johnson vaccine works similarly to the Moderna and Pfizer vaccines — it causes cells to produce the coronavirus’ “spike” protein, said Dr. H. Dirk Sostman, president of the Academic Institute at Houston Methodist,

However, it does this in a slightly different way.

Instead of using messenger ribonucleic acid (RNA) to deliver the instructions, it uses a DNA construct that produces the RNA in people’s cells, Sostman explained.

Also, rather than using an artificial lipid nanoparticle as a carrier like the Moderna and Pfizer vaccines, it uses an adenovirus as a carrier.

Though adenoviruses are common causes of diseases — such as the common cold — they are inactivated in the vaccine and cannot cause illness, explained Dr. Niraj Patel, who chairs the American College of Allergy, Asthma and Immunology COVID-19 Vaccine Task Force.

So, while Johnson & Johnson’s is a bit more complicated in how it delivers its payload, it accomplishes the same goal: safely triggering an immune response to the SARS-CoV-2’s spike protein.

Patel noted that in the phase 3 trial of the Johnson and Johnson vaccine, which included 40,000 participants, the vaccine was 66 percent effective in preventing moderate to severe COVID-19 disease.

Further, it was 85 percent effective in preventing severe disease.

“While this may seem disappointing compared to the Pfizer and Moderna, which reported about 95 percent effectiveness in preventing moderate to severe disease, the efficacy of the annual influenza vaccine averages about 60 percent,” said Patel, “and does prevent a significant amount of illnesses and hospitalizations annually.”

He added, “Any vaccine that reduces the burden of severe disease due to COVID-19, like the Johnson & Johnson vaccine, is going to help fight the pandemic.”

Also, the Johnson & Johnson vaccine has the advantage that it is a single-dose vaccination, he said.

Both Pfizer and Moderna require two injections.

Patel said that while it’s possible people may begin to request a particular vaccine based upon efficacy data, it is unlikely there will be a real choice in which to receive.

“At this time, it is expected that there will continue to be a limited supply of vaccine available until production can meet the overall demand,” he said.

Because of this, people will probably receive whatever vaccine is available at that time.

In the future, variables such as whether it’s difficult for an individual to get a second dose or temperature requirements for vaccine storage may factor into which vaccine a person might get.

Sostman said yes, it will be possible to take a different type of vaccine later.

“Getting one kind of COVID-19 vaccine does not make it unsafe or ineffective to get a different kind later,” he explained.

However, if receiving the Pfizer or Moderna vaccine for the first two shots, people should stay with the same vaccine. It is unknown if the effectiveness is the same with a mixed series.

“As far as future boosters, since the vaccine updates will be based on the current vaccines, it may make sense to stay with the same one you started with, but likely this will be less critical,” he said.

Sostman said that what boosters will look like in the future is unknown, but they may need to be updated each year, similar to flu vaccines.

Both experts emphasized that the vaccines are safe, and despite what is often shown in the media, severe allergic reactions are rare.

Maybe 5 per million will have a severe allergic reaction, Sostman said.

People with histories of severe allergies should tell their vaccination provider and speak with an allergist before obtaining a vaccination.

No other serious problems have been shown to be related to the vaccines, he said. The most common side effects include local reactions, such as a sore arm, swelling, fatigue, and headaches.

The side effects usually last one to two days and can be controlled with over-the-counter medications like acetaminophen (Tylenol) or ibuprofen (Motrin).

When compared with the genuine risks associated with COVID-19, these risks are small.

There is a 10 percent risk of being hospitalized with COVID-19, Sostman explained.

Also, if you are hospitalized, there is a 10 percent risk of dying.

Also, there are high risks of having long-term complications such as chronic fatigue, “brain fog,” or heart problems.

“Keep in mind that more than 440,000 people have died from COVID-19 in the U.S.,” Sostman said. “Don’t add to this grim total. Get vaccinated as soon as you can.”