Covid-19: ‘We have to ask ourselves what acceptable mortality rates are’

As restrictions slowly begin to be lifted in Ireland in tandem with increased vaccination, the question on everyone's lips is this: when will this pandemic be over?

As Covid fatigue dominates everyday conversations, what – if any – are the signs that will offer us a sense of safety and allow things go back to normal?

The first and most obvious sign will be declining numbers of people admitted to hospital with Covid-19 or, more specifically, declining numbers in intensive care units (ICUs) and fewer people dying from the disease.

"Results from Covid-19 vaccine trials in Scotland and Israel have found that the vaccines are 100 per cent effective against hospitalisation and mortality in the over-65s," says Dr Eoghan de Barra, infectious disease consultant at Beaumont Hospital and senior lecturer in the department of international health and tropical medicine at the Royal College of Surgeons in Ireland. In other words, nobody over 65 ended up in hospital or died from Covid-19 following vaccination.

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However, most of these vaccine trials took place before the new Covid-19 variants appeared and concerns have already been raised about whether some of the current vaccines will work against the newest strains of Covid-19 circulating. For this reason, vaccines against newer strains are already in production.

Dr de Barra says that while mortality rates will decrease significantly in the over-65s following vaccination, Sars-CoV-2 [the virus which causes Covid-19] will remain in circulation and many vulnerable individuals will continue to be at risk of severe disease or death from Covid-19.

There are young people in Ireland with undiagnosed hypertension and diabetes and obesity who will be vulnerable to Covid-19 when society opens up

International studies have confirmed that over 90 per cent of deaths from Covid-19 occur in those over 65. In Ireland, 1,992 people 85 and over died from the disease between March 2020 and March 2021. A total of 1,585 people aged 75-84 and 720 people aged 65-74 died here from Covid in the same period. This represents about 92 per cent of all deaths from Covid-19 in Ireland.

According to the Health Protection Surveillance Centre, 86 per cent of those who died from Covid-19 had an underlying condition. And, significantly, the so-called case fatality ratio (deaths per number of cases) dropped from 1.88 per cent of cases in March 2020 to 0.03 per cent in March 2021 in the entire population.

‘Acceptable mortality’

"We have to ask ourselves what will be the acceptable mortality rates for Covid-19. The World Health Organisation has defined the infection/fatality rate for under-70s as 0.05 (50 people in every 100,000) but we must remember that we still have a large proportion of the global population susceptible to Covid-19," says Dr de Barra. An average flu season in Ireland results in a death rate of approximately two people in every 100,000.

In Ireland, the under-65s represented 8 per cent of all deaths (368 out of 4,667) from Covid-19 in the first year of the pandemic. Yet, Dr de Barra points out that when society opens up further, there will still be a significant number of people vulnerable to serious illness from Covid-19 who don’t even come under the radar of the health services.

And for some of these people, Covid-19 might prove fatal. “Firstly, you’ve got to consider that while obese individuals (defined as those with a body mass index over 40) only accounted for 342 of all cases, almost half of them were admitted to hospital, one-third of them were in ICUs and one in 10 of them died. There are young people in Ireland with undiagnosed hypertension and diabetes and obesity who will be vulnerable to Covid-19 when society opens up,” says Dr de Barra.

And consider that while the risk of dying from Covid-19 might be very low (nine in every 100,000) for a young man or woman in their 20s, that person can still transmit the virus to a more vulnerable person who might not have yet been vaccinated.

Add to this the potential that current vaccines might not work for variants which haven’t even arrived in Ireland yet – and you begin to understand that we are further from the end of the pandemic than it might seem.

Most infectious disease specialists, virologists and epidemiologists now agree that Covid-19 is likely to become endemic in society. In a survey of scientists in Nature journal, 89 per cent said that Sars-CoV-2 was either very likely or likely to become an endemic virus. This means that it will never completely disappear but will continue to circulate in populations where many people are either immune to it through natural infection or from vaccination. Influenza and four other human coronaviruses that causes common colds are also endemic but a combination of annual vaccines and acquired immunity means that societies tolerate these seasonal deaths and illnesses they bring without requiring lockdowns, masks and social distancing.

Fatality rate

"Other pandemics such as Sars or Mers burned out because they had a higher fatality rate. Only two infectious diseases – smallpox and rinderpest – have been completed eradicated. Some have been eliminated from a geographical area – for example Covid in Australia – but it will come back when restrictions ease," says Dr de Barra.

"Covid-19 has partly become a pandemic because there is a low fatality rate, particularly if you consider that studies in China found that 82 per cent of people didn't have any symptoms," he adds.

Once a significant proportion of the population has been vaccinated, the future level of circulation of Sars-CoV-2 is expected to decrease but not disappear. “The herd immunity [threshold] depends on the reproductive rate of the virus and the B117 variant has a higher reproductive [transmission] rate. So, a higher percentage of the population – more than 70-80 per cent – will need to be vaccinated if variants are circulating,” says Dr de Barra.

It will require work to keep the virus at a tolerable level. The virus is unpredictable

“Getting the last 15-20 per cent of the adult population vaccinated is the hard bit. Vaccination is for preservation of life and the prevention of transmission. The ongoing circulation of the virus will reinfect those who the vaccination doesn’t work for or those who haven’t got the vaccination,” he says.

Vaccine-resistant variants

So, arguably, tracking down the virus will become even more important as case numbers decline. “When ICU and hospital admissions with Covid-19 are low, that’s the time to identify the five to 10 cases a day,” says Dr de Barra. In other words, testing, contact tracing and isolating those with the virus will need to be continued even when a high percentage of the population is vaccinated.

So this means that vaccination will not be the panacea to end the pandemic that some might have thought. "It will require work to keep the virus at a tolerable level. The virus is unpredictable. We're likely to have active genomic surveillance of vaccine-resistant variants. Europe is likely to contain the virus to a tolerable level but it will take a lot longer for the rest of the world to get to that point and we may need a vaccine booster in the next 12 months," says Dr de Barra.

Public health experts have pointed out that the behaviour of the public will be what will bring a fourth wave of Covid-19 to Ireland or allow us to become a low Covid country going forward.

So, these are the questions we have to ask ourselves. Will we continue to prevent the spread of the virus with all the infection control measures we have become familiar with? Will mask-wearing and social distancing outside our immediate family circle become a longlasting habit to prevent new variants of Covid-19 taking hold? Will we continue with coughing and sneezing etiquette and hand-washing next winter when Covid-19 is likely to join flu as a chronic seasonal illness? Will we work from home if we are feeling sick? Will vulnerable people avoid crowded places and travelling to far-flung destinations?

And, in the long term, will our children build up natural immunity to Covid-19 as they do for many other endemic viruses? Or will they too need to be vaccinated with the rest of the population on an annual basis? Only time will tell.