If you’ve been following the news, then you may have heard conflicting information about how soon a COVID-19 vaccine will become available. Unfortunately, my crystal ball is hazy on that front, but I think it’s fair to say that whenever a COVID-19 vaccine or vaccines first come out, initial supplies will be limited and focused on front-line healthcare workers, other essential workers, and people at high risk of severe COVID-19 infection. It may be several months before we have widespread COVID-19 vaccine available, so keep wearing face masks and social distancing until then!
Although there are still a lot of questions about when COVID-19 vaccine will come out, we’re starting to get a clearer picture of which COVID-19 vaccines may be available. There are currently four U.S. COVID-19 vaccines in the third (and final) phase of clinical trials prior to approval. It’s important to keep in mind that not all vaccine candidates will necessarily be approved; the whole point of a clinical trial is to study whether a vaccine is safe and effective in as many populations as possible. This post summarizes the four vaccines that are currently farthest along, but it’s no guarantee that any of them will ultimately be approved.
The Moderna and Pfizer/BioNTech COVID-19 vaccines both use similar messenger RNA (mRNA) technology. Messenger RNA carries the genetic “code” to teach cells how to make a particular protein – in this case the spike protein on the outside of the virus that causes COVID-19. Vaccinated people develop antibodies to the spike protein which hopefully will translate to immunity to the virus itself. Afterward, the mRNA is naturally broken down and cleared from the body.
Both the Moderna and Pfizer/BioNTech early clinical trials showed that vaccinated people developed antibodies against the spike protein. However, vaccinated people reported more fatigue, headache and pain at the site of the shot than people who received a placebo (a shot that did not contain any vaccine). Most side effects were mild or moderate, and most went away within two days.
The Moderna and Pfizer/BioNTech vaccines are both expected to need two doses to work completely. They both need to be frozen, possibly on dry ice, which may limit the locations that can store them appropriately. But, they might be the first vaccines available, when supplies are limited.
The AstraZeneca/University of Oxford COVID-19 vaccine uses a weakened adenovirus as a “vector” to carry the genes for the spike protein. Similar to the mRNA vaccines, vaccinated people develop antibodies to the spike protein, and the weak adenovirus breaks down without spreading further. Early clinical trials found that nearly all vaccinated people developed the antibodies, and severe side effects were rare. However, the AstraZeneca/Oxford Phase 3 clinical trials were briefly paused after a participant became sick with an unexpected severe illness. It’s since been approved to restart in the United Kingdom and the U.S.
Like the mRNA vaccines, the AstraZeneca/Oxford vaccine is expected to need two doses for full effect. However, it’s expected to be refrigerated at similar temperatures to other vaccines, which means that many more healthcare providers will be able to carry it. However, I hope that FDA regulators and vaccine experts closely review the safety data given the concerning illness that led the researchers to pause the study.
One more COVID-19 vaccine started phase 3 studies last week, in an exciting development. Johnson & Johnson/Janssen Pharmaceutical‘s COVID-19 vaccine also uses a weakened adenovirus vector, similar to the AstraZeneca/University of Oxford vaccine. In contrast to the other three COVID-19 vaccines, Johnson & Johnson/Janssen’s vaccine is expected to only need one dose. Although it’s starting phase 3 studies later than the other COVID-19 vaccines, the one-dose study might be faster than the two-dose studies. Additionally, the manufacturer has committed to making 1 billion doses per year, so it might be widely available when it is released.
So far, Johnson & Johnson/Janssen haven’t published the results of their early clinical trials, so I don’t have information yet on their vaccine’s safety and effectiveness. However, they reportedly plan to publish their first article soon; I’ll add an update after it’s released.
These four vaccines are the farthest along, but there are others under development. Novavax has COVID-19 vaccine studies in the United Kingdom that are expected to start in the U.S. in October, and Merck has two COVID-19 vaccines under development. There are also several COVID-19 vaccines in development in other countries. Hopefully there will be several safe and effective COVID-19 vaccines available within the next few months.
Stay safe and healthy,
💉 Dr. B