The Pfizer\BioNTech and Moderna messenger RNA (mRNA) vaccines are already available for some people. They require two injections and look better all the time, with very few serious reactions so far and good antibody response for prevention of COVID-19.
Two more vaccines appear ready to be available soon for public immunization. These not-yet approved vaccines, Johnson & Johnson/Janssen and AstraZeneca/Oxford, are different from the Pfizer and Moderna vaccines:
• The Johnson & Johnson/Janssen uses a virus called Adenovirus 26 that causes colds or flu-like symptoms (NEJM, Jan 13, 2021), while
• The Astra/Zeneca/Oxford vaccine uses a chimpanzee common cold virus (Lancet, Jan 9, 2021;397(10269):99-111).
Both of these new vaccines will help to protect you from COVID-19 because they contain the same gene (as the Pfizer and Moderna vaccines) for the spike protein that gets the COVID-19 virus into human cells. However, they have the spike protein added to two different viruses, while the Pfizer and Moderna vaccines contain no viruses whatever.
• The advantage of using viruses is that the virus vaccines are far more stable because they work through DNA instead of the less-stable mRNA for the spike protein.
• They are also more stable than the mRNA vaccines because the virus’s outer protein coat helps to protect the genetic material inside the cells, so they do not need to be frozen and can be refrigerated for three months at 36–46 degrees Fahrenheit (2–8 degrees Celsius). The mRNA vaccines are very unstable and have to be frozen at low temperatures.
• The viruses used in the Johnson & Johnson and AstraZeneca vaccines can enter human cells but cannot reproduce and therefore will not cause an infection.
• After the viruses enter a human cell, they then go inside the cell nucleus.
• The viruses contain the gene for the coronavirus spike protein and the invaded human cell makes copies of the coronavirus mRNA to make lots of new spike proteins.
• Then the human cells recognize that the spike protein is a foreign protein and treat it like an invading germ and destroy it.
• After you receive the vaccine, your immune system will work to destroy the spike protein when and if it tries to get into your own cells in the future.
Current Status of the Johnson & Johnson Vaccine
J&J has reported the results of their trial that included 402 people, ages 18 to 64, and 403 people over age 65. Some of these subjects also received a second dose 56 days later. Side effects included: injection site pain which usually resolved within 24 hours, fever, fatigue, headache, and muscle pain. By day 57, all volunteers had detectable antibodies, regardless of vaccine dose or age group, and remained stable for at least 71 days in the 18-to-55 age group (NEJM, Jan 13, 2021). The vaccine appears to be effective as both low and high doses caused a lasting high rise in protective S-binding and neutralizing antibodies in more than 90 percent of the trial subjects, for at least 71 days.
J&J expects its single dose vaccine to be available in March 2021. The Department of Health and Human Services announced it already has a deal with Janssen, J&J’s pharmaceutical subsidiary, worth about $1 billion for 100 million doses of its vaccine. The government has an option to buy an additional 200 million doses.
Current Status of the AstraZeneca Vaccine
The AstraZeneca/Oxford vaccine appears to be safe and effective (Lancet, Jan 9, 2021;397(10269):72-74). Four randomized, controlled trials conducted in the UK, South Africa, and Brazil report safety and benefit of the AstraZeneca chimpanzee adenovirus vaccine for adults aged 18 years and older (Lancet, 2020; 396: 313-319). The vaccinated people had:
• No COVID-19-related hospital admissions
• Short term protection for a single dose, with protective antibodies after 21 days
• Protective antibodies 14 days after the second dose in the two dose group
• No deaths from the vaccine
• The same number of serious side effects in the vaccinated and placebo groups
• Serious events included one case of transverse myelitis occurring 14 days after booster vaccination. However, two additional cases occurred in a control patient and a patient with pre-existing multiple sclerosis.
The AstraZeneca vaccine is expected to be given in two doses 28 days apart. Data to receive emergency use approval in the U.S. has not yet been submitted, but may be ready in late Spring 2021.
At present there is a shortage of available vaccines, but more than 200 different companies are working hard to develop new vaccines to help prevent COVID-19. While you are waiting your turn to be vaccinated, make sure that you follow all the rules for keeping yourself protected from becoming infected: restrict being in indoor places where people congregate as indoor air is the main source of infection, wear a mask, keep at least six feet away from people who are not in your immediate household, and wash your hands frequently.