A single study from Portugal has set off alarm bells about how the current dominant Covid variant may increase the risk of hospitalisation.
The study compares BA.2, an Omicron sub-variant – also known as the “stealth” variant – with BA.5, the Omicron sub-variant which is responsible for 78.8% of UK infections right now.
But just how much weight does this study carry?
Here’s what we know so far.
What does the research say?
A study in Portugal, published on the Medrxiv preprint server, collected 27,702 samples between April 25 and June 10 this year.
Slightly over half (55.5%) were classed as BA.2, and the rest BA.5, which is currently the dominant strain in many countries including the UK.
The scientists behind the study claim a BA.5 infection is 3.3 times more likely to mean someone has to be hospitalised compared to its predecessor.
They also found there was a higher risk of reinfection with BA.5 compared to the previous dominant strain, BA.2, regardless of vaccination status.
The researchers also claimed that, while jabs are less effective than they were against BA.2, booster vaccines still offer substantial protection against severe outcomes following BA.5 infection.
Irina Kislaya from the National Institute of Health in Lisbon worked on the research, and said: “Our results suggest that higher immune evasion of BA.5 might explain the surge in cases seen in countries with high BA.5 prevalence.”
Another study from Denmark found a lower rate of difference between the two sub-variants, but still noted that hospitalisation rates from BA.5 were 1.65 times higher than with BA.2.
Why do we need to be cautious about this research?
The Portugal study has not yet been peer-reviewed, meaning it should not yet be used to guide clinical practice, but was published due to its timely nature.
Professor Paul Hunter of the University of East Anglia also warned that both the Portugal and Denmark study are at risk of exaggerating hospitalisations because fewer tests are being conducted now, compared to when other strains were dominant.
With fewer tests being carried out, there may be a skew towards the more severe infections which result in hospitalisations while milder cases slip under the radar.
According to the i, Prof. Hunter said: “It doesn’t look like we will see a much higher hospitalisation rate than we saw with BA.2 but some increase is still possible.
“This isn’t to say BA.5 is associated with an increased risk of hospitalisation – but it’s early days yet.”
He said it would not be possible to know the precise risk until the end of this wave – but it’s likely that the hospitalisation numbers will remain much lower than in the most deadly waves seen earlier in the pandemic.
Still, UCL’s Professor Christina Pagel said: “On the increase in risk from hospitalisation, the most concerning about it is that it shows again that it is not true that each successive variant must be intrinsically milder from now on.”
What do we already know about BA.5?
We know that BA.5 grew 35% faster than BA.2, according to the UK Health Security Agency, and there was an uptick in hospitalisations when this sub-variant first became dominant.
However, they may have been caused by the surge in the new variant cases rather than because BA.5 is more likely to cause hospitalisations.
BA.5 spreads very easily and appears to somewhat dodge antibody responses from both those who have natural immunity and have been fully vaccinated.
It’s thought this is down to a mutation on its spike proteins, which enables the virus to retrain attacks on human lung cells.
Despite the fresh concerns around the new sub-variants, the UKHSA claimed in June there is “currently no evidence” they cause more serious illness than previous strains, or come with new symptoms.
Breathlessness and a loss of taste or smell were more common with previous strains of the virus, such as Alpha.
Symptoms include:
Cough
Runny nose
Sore throat
Fatigue
Headache
Muscle pain
Sneezing
Pain
What do the experts say?
ZOE Health Study experts told HuffPost UK that there is currently not enough data on their app to back up the claim of increased hospitalisations with BA.5.
However, Dr Denis Kinane, the founding scientist at Cignpost Diagnostics, told HuffPost UK: “This latest research is very concerning.
“While rising case numbers are always a worry, the biggest concern is increasing hospitalisation. While this is only a single study, it is a stark reminder that Covid is not over.”
Dr Kinane also claimed that as universal free testing has been scrapped in the UK, fewer people are likely to be diagnosed, making it hard to track Covid.
He pointed out: “The virus has not disappeared, it has continued to mutate, and though the UK’s vaccination programme allowed us to exert a reasonable amount of control on the virus’ transmission, waning immunity from the vaccine is now causing an uptick in hospitalisations, all of this has been borne out by the Portuguese study of BA.5.”
The last national booster rollout took place last winter, meaning the majority of the population are roughly six months on from their last vaccine dose making them more susceptible to the virus.
Dr Kinane issued a stark warning about the future of Covid too, telling us that we have “limited visibility on the virus’ prevalence in the population” meaning cases could keep climbing.
“We are also likely to see more mutations and recombinant variants of this virus if sections of the population remain unvaccinated or immune status wanes,” he added.
“It is expected that Covid will adapt, and we need to remain cautious about its evolution.”
Where are we with Covid right now?
The Office for National Statistics has identified more than 22,000 fatalities linked to Covid in England in the last six months.
At the end of May 2022, 2.98 million adults in England were still unvaccinated, while an extra 1.5 million have only had a single dose. Vaccines help reduce hospitalisation rates, although do not prevent people from catching the virus altogether.
Dr Kinane also warned that summer festivals and major events are likely to trigger a surge in infections.
