Unfortunately, vaccination rollout has been slow across the country, and both the Pfizer and Moderna vaccines are currently in limited supply. However, the potential for additional vaccines to receive FDA emergency use authorization in the near future should mean that more vaccine doses will become available and more people can be vaccinated.
According to the Centers for Disease Control and Prevention (CDC), phase 3 clinical trials are in progress or being planned for three more COVID-19 vaccines:
- University of Oxford/AstraZeneca COVID-19 vaccine
- Johnson & Johnson/Janssen COVID-19 vaccine
- Novavax COVID-19 vaccine
Unlike the Moderna and Pfizer vaccines, the three new vaccines are not messenger RNA (mRNA) vaccines - a new type of vaccine that uses genetic material from the virus that causes COVID-19 to give the body instructions for how to make copies of the spike protein unique to the virus. Recognizing that the protein should not be there, the body creates protective antibodies that will remember how to fight the virus in case of future infection.
Adenovirus viral vector vaccines
Both the University of Oxford/AstraZeneca and Johnson & Johnson/Janssen COVID-19 vaccines are adenovirus viral vector vaccines. These vaccines use adenovirus - a harmless common cold virus - that has been altered to deliver a piece of genetic code to our cells to mimic coronavirus infection. The cells make the surface spike protein of the coronavirus and then the immune system responds, priming it to attack any future coronavirus infection.
The Oxford/AstraZaneca vaccine requires two doses given four weeks apart, and the Johnson & Johnson/Janssen vaccine will only require one dose. The CDC reports that viral vector technology was used in Ebola vaccines and several studies of vaccines to combat other infectious diseases, such as Zika, the flu and HIV.
Protein subunit vaccine
Novavax's COVID-19 vaccine is a protein subunit vaccine. This type of vaccine combines a boosting agent with a component (subunit) from the spike protein in the coronavirus that causes COVID-19. When the vaccine enters the body, an immune response to the spike protein is triggered and antibodies are created to fight future infection.
Protein subunit vaccines are known for their effectiveness and used to prevent hepatitis B, flu and HPV. The Norovax vaccine will be given in two doses, 21 days apart.
Neither viral vector nor protein subunit vaccines require the cold storage temperatures that the two mRNA vaccines require. This might make the new vaccines appealing to small hospitals and health care providers in rural communities that may not have the proper equipment needed to store the Pfizer and Moderna vaccines already in use.
Importance of vaccination combined with precautions
Regardless of which vaccine people end up receiving, it is important to note that all vaccines given FDA emergency use authorization will be safe and effective at preventing COVID-19. What's more, neither of the two vaccines currently in use, nor the new vaccines in phase 3 trials, can cause people to become sick with COVID-19. All vaccines carry the risk of mild to moderate side effects.
Experts stress that vaccinating a majority of the population combined with the precautions we are already taking to slow the spread of COVID-19 is key to stopping the pandemic. So, even after vaccination, people are encouraged to continue to wear a face mask, keep a safe social distance, avoid large crowds and frequently wash their hands.
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