The health authorities are trying to find out what lies behind the recent spike in COVID-19 cases among those aged over 80, despite the number of infections in the general community going down.
Among the factors being considered are waning immunity from the booster vaccine and delayed impact of the new, highly transmissible Omicron variant of the virus.
Times of Malta reported on Friday that the weekly infection rate among those 80 and over had risen to an all-time high while other age groups registered drops in their rates.
Two potential culprits
Epidemiologist Neville Calleja said the health authorities were studying the situation in order to understand the reasons for the increase among this cohort.
He said the authorities were looking at two possibilities – that immunity from the booster dose might be waning and that the wave sparked by Omicron was only now hitting the elderly.
“One has to keep in mind that in general, the elderly cohort tend to have fewer social interactions than young people and so it is fair to speculate that while they were shielded earlier on, they are now experiencing the spike,” Calleja said of the link to Omicron.
While it was too early to clearly establish whether the higher rate of infection could be the result of waning immunity from the booster, Calleja said this was not being ruled.
The elderly started receiving their boosters as early as September when it became evident that resistance to the virus from the first doses had started to decline.
Unchartered territory
Calleja also noted that, as has been seen since the start of the vaccination roll-out in 2021, the elderly tend to respond less to the vaccine than younger cohorts.
This means it is more likely for immunity to wane sooner than in other age groups, he said.
And since Malta was among the first countries to administer booster doses, the health authorities are navigating “uncharted territory” – it could not yet compare its data to other countries.
He said it would be crucial to keep the hospital and mortality rates in mind when looking at the overall situation, especially if the number of those admitted or those who died remained stable despite the spike.
Recent global statistics have shown that while infection rates have increased dramatically, hospitalisation rates have stayed low compared to previous waves of the virus.
Malta has experienced a similar trend. During the second week of January, Malta’s weekly hospitalisation rate stood at 9.33 patients per 100,000 people while the mortality rate was 73.8 per 1,000,000 people – far lower than in the past when case rates were higher.
Scientists are attributing this trend to what evidence shows to be the milder variant, coupled with immunity from vaccines and previous infection.