In the latest installment of our “Hope Behind the Headlines” series, we look at the SARS-CoV-2 vaccine trials that have been progressing successfully, and at one promising therapeutic approach for COVID-19: Convalescent plasma therapy.
All data and statistics are based on publicly available data at the time of publication. Some information may be out of date.
The COVID-19 pandemic has been taking its toll on the world for months now, but researchers have not been sparing any time or resources in looking for ways to defeat the new coronavirus that causes this disease.
Once every 2 weeks at Medical News Today, we review the most promising findings and scientific advances in the fight against SARS-CoV-2.
Previously, we looked at new drug candidates for the treatment of COVID-19, and at some helpful research approaches for scientists studying the virus.
In this feature, we update you on the progress of some of the most hopeful vaccine and therapy trials so far.
In a study paper appearing in Science on May 20, researchers from Harvard Medical School in Boston, MA, and other collaborating institutions report that they obtained promising results with a DNA vaccine that they trialed in rhesus macaques.
DNA vaccines are relative newcomers in the field of vaccine research. They work by introducing DNA molecules into the body, meaning to stimulate an immune response to markers of a specific virus.
In the study in Science, the research team developed six different DNA vaccines with the role of eliciting an immune response against the spike protein of SARS-CoV-2 — in other words, the protein that allows this virus to infect healthy cells.
The researchers injected 35 rhesus macaques with the various DNA vaccine iterations and then infected them with the new coronavirus to see whether and which of the vaccines were effective.
They found that one of the six vaccines — which encoded the full length spike protein — had a greater protective effect than the other candidates.
While the vaccinated monkeys did develop mild symptoms consistent with SARS-CoV-2 infection, they also developed neutralizing antibodies — or the molecules that are able to recognize and fight the virus.
Thus, these monkeys presented an immune response to SARS-CoV-2 that was similar to the one seen in nonhuman primates and humans who have recovered from an infection with the new coronavirus.
The researchers also saw that monkeys that they had vaccinated had a lower viral load than unvaccinated monkeys, following infection with SARS-CoV-2, which suggests a more robust immune response in the former.
From their observations, the investigators conclude that their vaccine candidate works primarily by inducing a rapid immune response upon the individual’s exposure to SARS-CoV-2.
“Further research will need to address the important questions of the durability of protective immunity and the optimal vaccine platforms for a SARS-CoV-2 vaccine for humans,” the team writes in the study paper.
A study that Nature recently accepted for publication is the work of researchers affiliated with Vir Biotechnology, a biotech company with headquarters in San Francisco, CA. This research has found a new lead for vaccines.
The authors argue that an antibody present in the blood of someone who had recovered from SARS — the disease caused by the coronavirus SARS-CoV — could also be effective against SARS-CoV-2.
In laboratory tests, the researchers pitted the antibody they call “S309” against both SARS-CoV and SARS-CoV-2. They found that it was able to neutralize both.
The investigators explain that they initially identified S309 in blood samples from a person who contracted SARS-CoV during the epidemic of 2002–2003.
While these are early days, the team suggests that this newfound knowledge may eventually help control the spread of SARS-CoV-2.
“Accelerated development of [monoclonal antibodies] in a pandemic setting could be reduced to 5–6 months compared to the traditional timeline of 10–12 months,” the authors hypothesize in their paper.
In a previous “Hope Behind the Headlines” feature, we reported on the start of phase 1 of the first human SARS-CoV-2 vaccine trial to take place in the United Kingdom.
Already at that stage, the researchers behind this endeavor were expressing “a high degree of confidence” in the vaccine they called “ChAdOx1 nCoV-19.”
The vaccine uses a weakened adenovirus — a common cold virus — carrying the spike protein of SARS-CoV-2. In injection form, its role is to “teach” the immune system to recognize the SARS-CoV-2 spike protein and fight the virus.
On May 22, researchers at Oxford University, where the trial is based, announced that phase 1 has ended, and they are now recruiting for phases 2 and 3.
While the investigators are still following up on the progress of participants who volunteered for phase 1, they are also now casting a wider net with their current recruitment process.
More specifically, the researchers are looking to relist older adults, 56 years of age and over, as well as children aged 5–12 years.
That is because, in phase 2 of the trial, the team wants to find out if the vaccine will have a different effect on the immune system of people belonging to various age demographics.
So far, evidence has shown that older individuals are at an increased risk of developing severe COVID-19, and some studies suggest that children may also be more at risk of contracting SARS-CoV-2 than officials previously thought.
That being the case, it is vital to understand how well a vaccine may be able to protect people of different ages from the virus.
For phase 3 of the U.K. trial, the researchers will recruit a considerably larger, representative cohort, to evaluate more thoroughly for the vaccine’s efficacy across age groups.
Also, on May 22, scientists from China reported in The Lancet that phase 1 of the first ever human trial of a SARS-CoV-2 vaccine had concluded in Wuhan.
This vaccine goes by the name of a “recombinant adenovirus type-5 (Ad5) vectored COVID-19 vaccine.” It is similar to the one scientists are testing in the U.K., and like the other experimental vaccine, it uses an adenovirus that “carries” the SARS-CoV-2 spike protein.
In phase 1 of this trial, the researchers tested whether the vaccine is safe and, if the participants tolerated it well.
The team now reports that, although many participants did report some adverse effects to various doses of the vaccine, these were typically mild-to-moderate and short lived, indicating that the vaccine was well-tolerated.
The investigators also analyzed blood samples they collected from the participants at regular intervals following inoculation.
These analyses revealed that many of the participants developed various antibodies able to identify or react to SARS-CoV-2. They also saw markers of a quick immune response, particularly in volunteers who had received high doses of the vaccine.
The study team hypothesizes that the vaccine may be not only safe but also effective, although they are yet to confirm the latter.
Currently, the researchers are recruiting for phase 2 of the trial and aiming to work with more volunteers 60 years of age or over to test the efficacy of the experimental vaccine in older adults.
MNT recently spoke to Dr. Arturo Casadevall, chair of the Molecular Microbiology & Immunology Department at Johns Hopkins Bloomberg School of Public Health in Baltimore, MD, about convalescent plasma therapy.
This therapeutic approach dates back a century. Its premise is to use antibody-bearing blood components from people who have recovered from an infectious disease to treat others who have just developed it.
Dr. Casadevall brought this approach to the attention of other experts in the United States in the context of the COVID-19 pandemic.
People who have recovered from COVID-19, Dr. Casadevall told MNT, do have neutralizing antibodies that could specifically fight SARS-CoV-2. Thus, transfusions with plasma (a component of blood) from COVID-19 survivors could help others fight the disease.
Dr. Casadevall said that in the U.S., almost 12,000 people have already received convalescent plasma therapy.
He and his colleagues, including immunology experts from various institutions, have conducted a study they based on the data of the first 5,000.
This study, which is available online in preprint form, suggests that convalescent plasma therapy is safe.
Going forward, the specialists investigating the merits of this form of therapy for treating COVID-19 aim to confirm whether it is as effective in fighting this disease as it is safe.
“[First,] you want to show safety. And then the question of efficacy will be coming in the next few weeks. Right now, the data [is] being analyzed. We are hopeful.”
– Dr. Arturo Casadevall
The fact that this therapy will rely on convalescent plasma from donors, something that is already available makes it a promising early defense against COVID-19.
The approach could eventually become one of many therapeutic options for people that contract the new coronavirus.