ACROSS AMERICA — As COVID-19 vaccination efforts continue across the country, people waiting to get vaccinated have many questions, including why some vaccines require two doses and some only require one.
Here are five things you need to know about the vaccine doses:
1. Why do some vaccines require two doses?
Two COVID-19 vaccines have been authorized for use in the United States — Pfizer-BioNTech and Moderna — and approval is pending for three more.
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The Pfizer-BioNTech vaccine requires two doses, given 21 days apart. The Moderna vaccine also requires two doses, given 28 days apart, according to the U.S. Centers for Disease Control and Prevention.
The second shot increases effectiveness. In studies, Pfizer’s vaccine was 52 percent effective after the first shot, but 95 percent effective after the second.
Of the other vaccines still in the approval process, only one requires a single shot. The Johnson & Johnson one-shot Janssen vaccine is deemed to provide strong protection against severe disease and death caused by COVID-19, according to an analysis released Wednesday by scientists with the Food and Drug Administration.
That determination is a critical step, setting the stage for final approval of a vaccine that is easier to use and that agency officials said could help speed vaccinations because it requires only one dose. The FDA has scheduled a meeting Friday to discuss the request for emergency-use authorization for the Janssen vaccine.
2. What is the difference between the two approved vaccines?
The difference between the Pfizer and Moderna vaccines isn’t significant. Possible side effects are similar with both — pain, swelling and redness in the arm where the patient received the shot; muscle and joint pain; fever and chills; and nausea or vomiting.
The Pfizer vaccine can be given to anyone over 16. The Moderna vaccine is for people 18 and older.
The time between the first and second shot differs — 21 days for the Pfizer vaccine versus 28 days for Moderna.
Both vaccines protect against severe disease in the small number of people who still develop COVID-19 after getting their shots. None of the people who developed COVID-19 after taking either vaccine in clinical trials required hospitalization.
3. How effective are the vaccines?
Both the Pfizer and Moderna COVID-19 vaccines are messenger RNA – or mRNA – vaccines that have been shown to be 95 percent and 94 percent effective, respectively.
“The bottom line is that while the vaccines may use different technologies to teach the human immune system to recognize SARS-CoV-2, any authorized COVID-19 vaccine will be highly effective at preventing one from getting sick or dying from COVID-19,” Dr. Anthony Fauci, chief medical adviser to the president, said in President Joe Biden’s exclusive op-ed on Patch.
“And so, regardless of whether it is a two-dose vaccine or a single-dose vaccine, get vaccinated as soon as any vaccine becomes available to you to protect against COVID-19,” he said.
Overall, the Johnson & Johnson vaccine is about 66 percent effective at preventing moderate to severe cases of COVID-19, and about 85 percent effective against most serious illnesses.
With different variants of the virus showing up around the world, the FDA cautioned that it’s yet unclear how well the J&J vaccine works against those mutations.
4. Are there any other vaccines?
There are a few vaccines that are currently in Phase 3 of clinical trials but have not yet been approved for use in the United States. Besides J&J’s Janssen vaccine, the others are AstraZeneca and Novavax vaccines.
As of Feb. 11, the World Health Organization’s Strategic Advisory Group of Experts on Immunization issued interim recommendations for use of the Oxford/AstraZeneca COVID-19 vaccine, but it has yet to be recommended for emergency use by the WHO.
5. How do mRNA vaccines work?
The mRNA vaccines contain genetic material designed to generate a protein called the “spike” protein found on the surface of SARS-CoV-2, the virus that causes COVID-19, according to Fauci. The immune system recognizes the spike protein as part of the virus and mounts a robust immune response that protects against the virus.
To be most effective, both of these vaccines require two shots. Multiple-dose vaccinations are not a new concept; for example, the vaccines for shingles, HPV, and hepatitis B also require multiple vaccinations.