Last updated on April 30, 2020
The last couple weeks we have discussed the importance of vaccines and anti-viral drugs—our arsenal of weapons against viral infection. This week, I want to zoom in a bit and specifically investigate what researchers are doing to develop tools to fight Covid-19. Currently, most people who are able to do so are staying home, in order to curb the spread of Covid-19. A vaccine, if it can get past clinical trials and be distributed to the general public, could allow for enough herd immunity for us to return to normalcy. But it takes a long time to verify that a vaccine works, and we still don’t know how long immunity to Covid-19 lasts. Anti-viral drugs for Covid-19 could help to reduce the death rate associated with the disease, particularly among the elderly and immunocompromised. For both vaccines and anti-viral treatments, it will take time and a considerable amount of money to get these drugs through clinical trials and to wide-spread distribution.
Since Covid-19 made its debut in January, researchers around the world have been studying it and developing potential drugs and vaccines. A company that specializes in mRNA, Moderna, developed a special mRNA vaccine that entered clinical trials back in March, a record speed for vaccine development. The vaccine utilizes mRNA that encodes for the spike protein on the virus’ surface. If you remember from my third blog post, mRNA is the same genetic material that the coronavirus uses. When injected into a patient, the mRNA gets taken up by surrounding cells and translated into the desired spike protein. Like most subunit vaccines, this technique relies on the ability of a small virus subunit to cause enough of an immune response to create antibodies.
The advantage of the Moderna vaccine, which allowed it to be developed so quickly, is that mRNA is comparatively cheap and easy to synthesize. This could be important down the line, when we need to manufacture and distribute the vaccine to as many people as possible. But before it can be distributed, the vaccine needs to be proven safe and effective. As of April 27th, Moderna has applied to start phase 2 clinical trials. These trials will test the vaccine in healthy individuals and track antibody levels over 12 months. Because of the nature of vaccine trials, it takes a while to determine the length of immunity and whether or not boosters are necessary.
The biggest problem with developing a vaccine is that scientists aren’t actually certain whether infected individuals are immune to reinfection or, if they are, how long that immunity lasts. Preliminary reports indicate that the presence of low levels of antibodies in a patient’s blood may not be enough to prevent reinfection. And information about the other coronaviruses, MERS and the original SARS, indicates that immunity to Covid-19 will likely only last 1-2 years at most. Best case scenario, this means that a Covid-19 vaccine will require yearly boosters. But if the disease itself doesn’t inspire at least a year of immunity from reinfection, then an inactivated or subunit vaccine has little chance of producing viable immunity. Only time can tell.
In the meantime, our best hope for combating Covid-19 is anti-viral drugs, particularly those that have already proven to be safe in humans. Two drugs have been identified for their potential to inhibit an enzyme important to viral infection—hydroxychloroquine and remdesivir. Hydroxychloroquine (HCQ) is a less toxic version of chloroquine, a potent anti-malarial drug. HCQ is already used to treat lupus and rheumatoid arthritis. In addition to inhibiting the infection rate of SARS-CoV-2, HCQ has proven anti-inflammatory properties, which may curb the immune system’s over-reaction to severe infection (often referred to as the “cytokine storm”). A cytokine storm is like the immune system’s version of carpet bombing, and it can be just as deadly as the virus itself. While HCQ may be a good immediate solution (and it is being used in severe cases), it can still be toxic in the long-term and has been linked to heart rhythm problems, so researchers are searching for a better option.
Remdesivir is an antiviral drug developed by the biotech company Gilead, originally to treat Ebola. Back in late February, the National Institute of Allergy and Infectious Disease started clinical trials to test the efficacy of the drug in treating Covid-19. As of April 29th, Gilead has announced the results of the third phase of those clinical trials indicating that a five-day course of the drug has been shown to reduce recovery time (the full report from the clinical trial has yet to be published). According to the NY Times, sources at the Food and Drug Administration (FDA) have indicated that the administration will likely announce emergency approval for the drug soon.
The results of the remdesivir drug trials are modest, but promising, with an average reduction of recovery time from 15 days to 11 days and a decrease in mortality rate from 11% to 8%. These results aren’t trivial, but they are unlikely to be a definitive solution to the pandemic. There are many more experimental drugs that are being developed and tested to fight Covid-19, which may prove more effective. But until they can be properly tested, they won’t be available for widespread use.
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