The World Health Organisation (WHO) officially declared COVID-19 a global pandemic on 11 March 2020. In the last twelve months, mankind has been dealt a heavy blow:119m people have been infected and over 2.6m have died. The good news is that science has made great progress to address this health crisis with at least seven different types of vaccines rolled out and over 300m doses administered as of 9 March 2021.
This rapid progress is in sharp contrast to the sixty-year battle to tame the Human Immunodeficiency Virus (HIV). The first HIV patient was identified in 1959 in the Democratic Republic Congo (DRC). The theory is that humans became infected after consuming chimpanzee meat contaminated with the Simian Immunodeficiency Virus (SIV) and that this transfer could have happened as early as in the 1920s. By 2019, there were 38m people living with HIV and 1.7m of those were infected in 2019 alone. Africa accounts for 68% of global HIV cases. There is still no vaccine or cure.
The contrast between these two deadly viruses begs the question: how was science able to succeed with COVID-19 but struggles to make meaningful progress with HIV?
Let’s start with the basics. How do viruses work?
Viruses are made of genetic material inside a protein coating which behave like ‘hijackers’. They invade living, normal cells in the human body and use those cells to multiply themselves. This can kill, damage, or change the cells and make the host sick.
The capacity of a virus to cause human diseases varies. Some viruses cause asymptomatic or mild infections while others result in rapidly progressive and fatal infections. For example, viruses that cause infectious diseases such as the common cold are typically mild while others such as HIV, Ebola, and SARS-CoV-2 can cause severe illnesses and death.
What are considered as the deadliest viruses in the world today?
Let’s talk about COVID-19
COVID-19 is caused by a virus known as the SARS-CoV-2 and spreads from an infected person’s mouth or nose in small liquid particles when they cough, sneeze, speak, sing or breathe heavily.
SARS-CoV-2 attaches to cells in the human body using a protein on its surface called spike. This spike protein binds to a protein molecule that’s found on the surface of human cells called the ACE2 receptor. After binding to ACE2, the virus undergoes a structural change that allows it to fuse with the cell and reproduce. The SARS-CoV-2 virus can lead to pneumonia, respiratory/heart/ liver failure, septic shock, and death.
Why is COVID-19 so deadly?
Many COVID-19 complications may be caused by a condition known as a cytokine storm. Cytokines are chemical signalling molecules that normally guide a healthy immune response. But in a cytokine storm, levels of certain cytokines soar far beyond what the body needs, and this causes immune cells to attack healthy tissue. Blood vessels leak, blood pressure drops, clots form, and catastrophic organ failure can ensue.
Why do some people die when they go on ventilators that are meant to save them?
For the most serious COVID-19 cases where patients are not getting enough oxygen, doctors may use ventilators to help a person breathe. Patients are sedated and a tube inserted into their windpipe is then connected to a machine that pumps oxygen into their lungs.
Although ventilators save lives, some patients do not survive, with research suggesting the odds worsen the older and sicker the patient. Infection is one potential risk associated with being on a ventilator as the breathing tube in the airway can allow bacteria to enter the lungs, which can lead to pneumonia. A ventilator can also damage the lungs, either from too much pressure or excessive oxygen levels, which can be toxic.
Nonetheless, ventilators can be lifesaving and many of those who have survived severe cases of COVID-19 would not have made it without one.
How was the world able to develop a vaccine in less than a year?
Four factors played a pivotal role in providing the capability for rapid COVID-19 vaccine development:
- previous research on related corona viruses which caused SARS (Severe Acute Respiratory Syndrome) and MERS (Middle East Respiratory Syndrome)
- faster methods for manufacturing vaccines
- enormous funding that allowed companies to run multiple trials in parallel
- regulators moving more quickly than normal
Should people who have had the virus still get the vaccine?
The short answer is yes. One should be vaccinated regardless of whether or not they have previously been infected with COVID-19 because it is unknown how long they would be protected from getting the virus again.
Biomedical research experts are still learning more about how long vaccines protect against COVID-19 in real-world conditions and will strive to keep the general public informed as new evidence becomes available.
How can the world build herd immunity?
Herd immunity occurs when enough people in a population have developed long-lasting immunity to a virus or disease, either through infections or vaccinations, that the virus cannot find new hosts and stops spreading, resulting in community-wide protection.
Scientists estimate that in the case of the coronaviruses, this threshold could be anywhere between 70-90% of a population. Vaccinations as opposed to natural infections can safely allow for herd immunity to be reached in a community.
It is important to stress that new coronavirus variants could undermine herd immunity protection, either by proving more resistant to existing vaccines or by finding a way to spread more easily.
Let’s switch gear and talk about HIV. How does HIV infect the body differently from COVID-19?
HIV targets and gradually weakens the body’s immune system by damaging white blood cells known as CD4 T cells. After attaching itself to a CD4 T cell, the virus merges with it and then multiplies, damages or destroys the cell, before moving on and targeting other cells.
This damage means that, over time, the body becomes less able to fight off other infections. If the immune system becomes damaged beyond a certain point, infections that are typically mild can be life threatening. These are known as opportunistic infections.
Why has it been so hard to find a cure or vaccine for HIV?
First, as no one has naturally recovered from HIV, researchers do not have a way to identify an immune response that would be effective against HIV.
A second challenge (related to the first) is that research has not been able to identify a specific immune response that is closely related to protection against HIV infection or disease. Because no one is known to have been infected with HIV and then naturally cleared the virus, we do not know what protection from HIV would look like in a human being.
A third challenge in developing a vaccine is that HIV mutates frequently. These frequent changes in the virus make it a moving target for a vaccine and poses yet another difficult challenge: a vaccine that protects against one HIV strain, may not provide protection against others.
Will we ever find a cure?
Over the course of several decades of HIV vaccine research, we have learnt a lot from animal studies, from investigations of people who have been exposed to HIV without becoming infected, and from clinical trials of experimental HIV vaccines. While no vaccine currently exists for HIV, scientists are becoming optimistic after the results of recent studies.
However, even if vaccine studies produce positive results in the next few years, this does not mean HIV vaccine research will stop. Further research will be needed to make the vaccines more protective, easier and cheaper to manufacture and to find out how to deliver them to the largest number of people in different regions of the world.
Having an effective vaccine is one challenge, but an additional major challenge will be ensuring that those who are at highest risk of contracting HIV can be vaccinated.
Is the world ready for the next pandemic?
Without a doubt, the world will have learnt from mistakes and shortcomings in the current COVID-19 pandemic. These will hopefully inform how to better tackle and manage future pandemics. In these efforts, science will need to be the ultimate guide.
The continual strengthening of existing health systems and social protection, support for communities on the frontlines, and technical cooperation for countries will be pivotal in ensuring we are ready to tackle the challenges future pandemics pose.
I am so proud to have a fellow Zambian at the heart of some of the most important battles of modern times. Any inspiring words for that young Zambians or Africans looking to join biomedical science?
I have been involved in biomedical research in infectious diseases since 2001, after witnessing the devastation caused by HIV in Zambia in the late 1980s and early 1990s. My undergraduate degree was a double major in biology and chemistry from the University of Zambia (UNZA). I then did a Master’s in Molecular Biology at the Vrije Universiteit Brussels and a PhD in Immunology at Oxford.
I was drawn to the science to try to develop a vaccine to prevent HIV which was destroying families and communities right in front of my eyes. I would encourage those looking to make a difference in biomedical research to carefully plan their academic career path and to always aim high in their pursuits. They should follow their passions and dreams of being a difference maker and try whenever possible to connect with people in the field that inspire them and can mentor them.