Global deaths from COVID-19 have reached 1 million, but experts are still struggling to figure out a crucial metric in the pandemic: the fatality rate - the percentage of people infected with the pathogen who die.
Here is a look at issues surrounding better understanding the COVID-19 death rate.
How is a death rate calculated?
A true mortality rate would compare deaths against the total number of infections, a denominator that remains unknown because the full scope of asymptomatic cases is difficult to measure. Many people who become infected simply do not experience symptoms.
Scientists have said the total number of infections is exponentially higher than the current number of confirmed cases, now at 33 million globally. Many experts believe the coronavirus likely kills 0.5 percent to 1 percent of people infected, making it a very dangerous virus globally until a vaccine is identified.
Frequently Asked Questions
A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.
There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.
Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.
Researchers have begun to break down that risk by age group, as evidence mounts that younger people and children are far less likely to experience severe disease.
"The death rate for people below age 20 is probably one in 10,000. Over the age of 85 it is around one in 6," said Dr. Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington in Seattle.
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What is a "case fatality rate"?
There has been an apparent decline in death rates when measured against the number of new infections confirmed by coronavirus testing. In places like the United States, that "case fatality rate" has fallen dramatically from 6.6 percent in April to just over 2 percent in August, according to Reuters statistics.
But experts said that the decline has largely been driven by more widespread testing compared with the early days of the pandemic, detecting more people who have mild illness or no symptoms. Improvements in treating the severely ill and protecting some of the highest-risk groups, are also credited with improving survival.
"We are much more aware of potential complications and how to recognize and treat them," said Dr. Amesh Adalja of the Johns Hopkins University Center for Health Security in Baltimore. "If you are a patient who gets COVID-19 in 2020, you would much rather get it now than in March."
What does that mean for individuals, and governments?
That highlights the need for continued vigilance, as some countries begin to experience a second wave of infections.
For example, researchers in France estimate that country's case fatality rate fell by 46 percent by the end of July compared with the end of May, driven by an increase in testing, improved medical care and a greater proportion of infections occurring in younger people, who are less likely to experience severe disease.
"Now, we are seeing a fresh rise in hospitalizations and ICU (intensive care unit) registrations, which means this discrepancy is about to end," said Mircea Sofonea, a researcher with Montpellier University in France. "We will have to understand why."
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