Nearly 15 million people were killed either by coronavirus or by its impact on overwhelmed health systems during the first two years of the pandemic,  the World Health Organisation estimates.

The estimate is more than double the current official death toll of just over six million.

Most of deaths occurred in Southeast Asia, Europe and the Americas, according to a WHO report issued on Thursday.

The director-general of the United Nation’s health agency, Tedros Adhanom Ghebreyesus, said the newly calculated figure was “sobering” and should prompt countries to invest more in their capacities to quell future health emergencies.

WHO tasked scientists with determining the actual number of COVID-19 deaths between January 2020 and the end of last year.

They estimated that between 13.3 million and 16.6 million people died either due to the coronavirus directly or because of factors attributed to the pandemic’s impact on health systems, such as cancer patients who were unable to seek treatment when hospitals were full of COVID-19 patients.

Based on that range, the scientists came up with an approximated total of 14.9 million.

The estimate is based on country-reported data and statistical modelling, but only about half of countries provided information.

The total number of deaths associated with #COVID19 worldwide from 2020-2021 may be closer to 14.9 million: New estimates by WHO & @UNDESA.

That’s 9.5 million more deaths than reported https://t.co/qDvaA6t5KZ #HealthData pic.twitter.com/ZjABJzlgiZ

— World Health Organization (WHO) (@WHO) May 5, 2022

WHO said it wasn’t yet able to break down the data to distinguish between direct deaths from COVID-19 and those related to effects of the pandemic, but the agency plans a future project examining death certificates.

Accurately counting COVID-19 deaths has been problematic throughout the pandemic, as reports of confirmed cases represent only a fraction of the devastation wrought by the virus, largely because of limited testing.

Government figures reported to WHO, and a separate tally kept by Johns Hopkins University, show more than 6.2 million reported virus deaths to date.

Scientists at the Institute of Health Metrics and Evaluation at the University of Washington calculated for a recent study published in the journal Lancet that there were more than 18 million COVID deaths from January 2020 to December 2021.

A team led by Canadian researchers estimated there were more than three million uncounted coronavirus deaths in India alone.

WHO’s new analysis estimated that missed deaths in India alone ranged between 3.3 million to 6.5 million.

In a statement following the release of WHO’s data, India disputed the agency’s methodology.

India’s Health and Family Welfare Ministry called the analysis and data collection methods “questionable” and complained the new death estimates were released “without adequately addressing India’s concerns.”

Samira Asma, a senior WHO director, acknowledged that “numbers are sometimes controversial” and noted that all estimates are only an approximation of the virus’ catastrophic effects.

“It has become very obvious during the entire course of the pandemic, there have been data that is missing,” Asma said on Thursday.

“Basically, all of us were caught unprepared.”

Dr Bharat Pankhania, a public health specialist at Britain’s University of Exeter, said the world may never get close to measuring the true toll of COVID-19, particularly in poor countries.

“When you have a massive outbreak where people are dying in the streets because of a lack of oxygen, bodies were abandoned or people had to be cremated quickly because of cultural beliefs, we end up never knowing just how many people died,” he explained.

Dr Pankhania said that while the estimated COVID-19 death toll still pales in comparison to the 1918 Spanish flu pandemic — which experts estimate caused up to 100 million deaths — the fact that so many people died despite the advances of modern medicine, including vaccines, was shameful.

He also warned that the cost of COVID-19 could be far more damaging in the long term, given the increasing burden of caring for people with long COVID.

“With the Spanish flu, there was the flu and then there were some (lung) illnesses people suffered, but that was it,” he said.

“There was not an enduring immunological condition that we’re seeing right now with COVID.

“We do not know the extent to which people with long COVID will have their lives cut short and if they will have repeated infections that will cause them even more problems,” Dr Pankhania said.