Group most at risk of being hospitalised and killed by Covid despite vaccination

There’s a minuscule chance of still dying from Covid-19 after getting vaccinated – and experts have identified which group is more susceptible.

The world is experiencing the largest vaccination event in history in its attempt to deal with the global coronavirus pandemic. But despite the marked effectiveness of the various vaccines, there is still a risk – albeit small – of “breakthrough” cases.

Now a new study has identified those unlucky few who are most at risk of ending up with a serious case of Covid despite having had the jab.

Some 5.7 billion Covid-19 vaccinations have already been administered worldwide. And their effectiveness is evident, as previously locked down nations begin to reopen and pressure on hospitals starts to ease.

According to data collected by the Royal Institution of Australia’s Cosmos magazine, 92 per cent of those dosed with AstraZeneca can fight off the virus before it gets bad enough for hospitalisation. In the case of Pfizer, that figure is about 96 per cent.

“It’s clear that the vaccines are highly effective, and without them we would be facing a much deadlier pandemic,” says Yale University associate professor of medicine (cardiology) Hyung Chun.

Vaccinated people can still end up in hospital with Covid – but the chances are very small. Picture: Jeff Pachoud/AFP

However, among the vaccinated, there will still be a few who still suffer severe illness. And these are who the Yale study has sought to identify.

Those most at risk of severe illness

Yale studied 969 instances of Covid-19 over 14 weeks between March and July in its local New Haven Health System.

Of these, just 54 had been fully vaccinated.

“The majority of fully vaccinated patients experience mild or no symptoms if infected with SARS-CoV-2,” Dr Chun says.

Of the 54 “breakthrough” cases, just 14 advanced to a severe stage.

Four ultimately needed emergency intensive care. Three died.

“These cases are extremely rare, but they are becoming more frequent as variants emerge and more time passes since patients are vaccinated,” Dr Chun says.

According to the study, most of the severe cases were aged between 65 and 95. Many had pre-existing conditions, especially type-2 diabetes and heart disease. Some had been taking immune-system suppressing medications.

Older people with pre-existing conditions such as type-2 diabetes and heart disease can still fall very ill with Covid even if they’re vaccinated. Picture: Suliane Favennec/AFP

Again, those “breakthrough” deaths must be put into perspective.

The US Centres for Disease Control and Prevention (CDC) said that, as of August 30, it knew of 12,908 vaccinated Covid-19 patients who had needed hospitalisation. Those who died amounted to fewer than 0.008 per cent of America’s vaccinated population.

Arms race

Dr Chun pointed out that many of the patients in the March to July study did not have the highly infectious Delta variant of Covid-19. How much this mutation has changed the equation is yet to be determined.

Covid-19 – essentially the same type of virus as the common cold – shows the same tendency to adapt to vaccinations over time. Exactly how fast and by how much remains to be seen.

Monash University virologist Dr Vinod Balasubramaniam says Delta has become the dominant variant worldwide, “causing spikes in new and breakthrough infections” among vaccinated populations.

“There is some indication that the Delta variant may also result in more severe disease,” he says.

Vaccines are still the best form of defence against getting severely ill with Covid-19.

And the imprint vaccines leave on the body’s immune system are not permanent.

The Royal Institution of Australia’s Elizabeth Finkel says a UK preprint shows Pfizer effectiveness waning from 90 per cent to 78 per cent after three months. AstraZeneca’s strength fell from 69 per cent to 61 per cent over the same time frame.

But Covid’s previous behaviour remains the best indicator of future trends.

Those most likely to be at risk of severe illness, Dr Chun says, are those with existing health conditions.

“Identifying who is more likely to develop severe Covid-19 illness after vaccination will be critical to ongoing efforts to mitigate the impact of these breakthrough infections,” the Yale report reads.

Future fight

“As effective as the vaccines are, with emerging variants and increasing cases of breakthrough infections, we need to continue to be vigilant in taking measures such as indoor masking and social distancing,” Dr Chun says.

Dr Vinod agrees: “We must first understand that the vaccines we have currently are not a miracle cure. They were designed to provide immunity against symptoms caused by the virus and the possibility of reducing transmission of the virus from person to person.”

Many researchers expect Covid-19 to become a seasonal infection, like the flu virus.

People will gradually develop a degree of immunity through both illness and vaccination, and this will protect most from severe disease.

But, like the flu, future Covid is still likely to have a severe impact upon some.

“Having had Covid-19 is unlikely to give you lifelong immunity,” says Dr Vinod. “But, even if you are infected again, the second infection will likely be less serious. We might need booster doses against variants and to provide optimal immunological memory against the disease.

“If SARS-CoV-2 experiences antigenic evolution at rates that are similar to influenza, annual shots for vulnerable populations may well be necessary.”

Jamie Seidel is a freelance writer | @JamieSeidel