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The Two-Dose COVID-19 Vaccine Facts

April 11, 2021 Posted in: Blogs , English

Because the situation surrounding COVID-19 is constantly evolving, some information may not be up to date. Stay informed by following information from your local officials and by visiting the CDC website.

The development of a third COVID-19 vaccine option by Janssen/Johnson & Johnson, which only requires one dose, has made the path to nationwide immunization more of a reality. With all of the information out on the Internet, it can be a little difficult to navigate what is fact and what is fiction. Is it necessary for you to get a second dose? What is there to know about the new single-dose vaccine? We are here to answer these questions to make the jumble of information a little clearer.

Why do some vaccines require two doses?

During the clinical testing of the Pfizer-BioNTech and Moderna vaccines, researchers found that the second dose provided a more effective immune response compared to the first dose alone. The first dose of these vaccines acts as a starting point for building protection against COVID-19. The second dose reinforces this protection, as explained by Dr. Kia Parsi, chief medical officer at St. Joseph Health.

“The recommendation is to get both doses to have the most effective immunity that you can achieve from the vaccine. It’s a very effective vaccine. If you get both doses, the studies show about 95% effectiveness to prevent any symptoms of COVID-19.”

-Dr. Kia Parsi

When do I get the second dose?

It is recommended to get the second dose of the Pfizer-BioNTech vaccine approximately 21 days after receiving the first dose and approximately 28 days for the Moderna vaccine. According to the CDC, the second dose should not be administered before this recommended time interval. If it is not feasible to obtain the second dose within this range and a delay is unavoidable, the second dose of Pfizer and Moderna COVID-19 vaccines may be administered up to 6 weeks or 42 days after the first dose, according to the CDC.

What level of immunity do I have after getting the vaccine?

Vaccination is the most effective way to be protected from a disease because it prepares your immune system to prevent illness.

Even though you need two doses of the Pfizer and Moderna vaccines to maximize immunity, clinical trials for each vaccine showed partial immunity after the first dose. The Pfizer-BioNTech vaccine demonstrated 52% vaccine effectiveness between the first and second doses. The Moderna vaccine had 50.8% vaccine effectiveness around 14 days after the first dose.

In order to receive the highest vaccine immunity levels, you should receive two doses of the Pfizer and Moderna vaccines. Vaccine effectiveness for the Pfizer vaccine showed to be 95% after receiving the second dose, based on the clinical trials. The Moderna showed 94% vaccine effectiveness after the second dose was administered.

What happens if I only get a single dose?

Some medical professionals are concerned about what could happen if people only get a single dose of the Pfizer or Moderna vaccines. As more people become infected with COVID-19 or receive the vaccine, they develop more antibodies to fend off the virus if they were to be exposed. Receiving only a single dose and being partially immunized allows the coronavirus to develop more variants. For Pfizer and Moderna vaccines, it is important to get the second dose in order to have the most protection the vaccine can offer. You won’t get the full duration of protection from the vaccines until one to two weeks after the second dose. For Janssen/Johnson & Johnson, only one dose is needed for immune protection to form in 28 days.

What is there for me to know about the new Johnson & Johnson vaccine?

The Johnson & Johnson vaccine is a single-dose vaccine, meaning you won’t have to go back for a second dose like with the Moderna and Pfizer vaccines. It has side effects similar to the Pfizer-BioNTech and Moderna vaccines, including moderate flu-like symptoms and swelling of the injection site. People with severe allergies who have experienced anaphylaxis in the past or allergic reactions to vaccines should talk to their primary care doctor about whether they should get the COVID-19 vaccine.

St. Joseph Health has been designated as a vaccine hub by the State of Texas. The main vaccination site is located at the Brazos Center in Bryan. After receiving your first dose, more information will be provided about scheduling your second dose. Request your COVID-19 vaccine with St. Joseph Health today. 



CDC | Considerations for Use of COVID-19 Vaccines in the US

Healthline | Why Do You Need Two Doses For Some COVID-19 Vaccines?

Johnson & Johnson | Vaccine Information

Scientific American | Is It Safe To Delay A Second COVID Vaccine Dose?

CDC | Types of Immunity

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