Age, sex, vaccine dose, chronic illness – insight into risk factors for severe Covid is growing
About 18.5 million individuals, or 24.4% of the UK population, are at increased risk of developing severe Covid because of underlying health conditions. It is well known that older people are at high risk, but the understanding of all the risk factors is incomplete. Experts say that this knowledge needs to develop at speed to support policy and planning given that social restrictions will end in England on 19 July.
Vulnerable people with underlying health conditions
The conditions most likely to be mentioned on death certificates where Covid-19 is mentioned are diabetes (mentioned on 21% of death certificates where Covid was cited), hypertensive diseases, chronic kidney disease, chronic obstructive pulmonary disease, and dementia. Several studies also report an increased risk of adverse outcomes in obese and morbidly obese people.
The British Heart Foundation said that experts had tested how vaccines worked in people with most health conditions, including heart conditions, and found the vaccines “just as effective”.
The foundation said: “The only possible exception is people who are taking immunosuppressants or who are immunocompromised. This is because they may not generate the same immune response to the vaccine. Research is being undertaken in the UK to better understand this. The vaccine is generally recommended for people who are immunocompromised or immunosuppressed.”
People who are not vaccinated or have had just a single dose
We know that the Delta coronavirus variant, which has spread across the UK, nearly doubles the risk of hospitalisation. Public health experts have found that people infected with the Delta variant were 85% more likely to be admitted to hospital than those infected with the Alpha variant.
With the elderly population better protected via vaccination, the majority of those in hospital are now younger than during previous Covid waves and have shorter stays.
But according to a Public Health England study published in May a single dose of either the AstraZeneca or Pfizer/BioNTech vaccine reduces by 33% the risk of developing symptoms due to the Delta variant. After two doses the Pfizer vaccine was found to be 88% effective against symptomatic disease from the Delta variant.
Almost 9 million of the 18.5 million at-risk individuals, based on current guidance across the UK, are aged over 69.
That means that 66.2% of individuals over the age of 69 are at risk, rising to a peak of 79.4% among those aged 85–89 in England. This compares with a national “at-risk prevalence” of 24.4% of the UK population considered at moderate or high risk.
Among people already diagnosed with Covid, people who were 80 or older were 70 times more likely to die than those under 40.
Of the national “at-risk prevalence” of 24.4%, children aged from two to nine make up 5.1%, and children across all school years make up 8.3%. “Kids can transmit the virus. They are susceptible to it,” said Anne Rimoin, an epidemiology professor at the University of California, Los Angeles.
More than 640,000 children in England were absent from school last week due to Covid-19. The number of schoolchildren with confirmed Covid infections rose from 15,000 on 24 June to 28,000 on 1 July, while the number self-isolating because of a suspected Covid contact within school rose from 279,000 to 471,000 last week. Including contacts outside school, more than 560,000 children were self-isolating.
In Florida, the number of children who had gone to hospital with Covid-19 surged by 23% in eight days last summer. And a South Korean study showed that children as young as 10 could transmit Covid within a household just as easily as adults.
The BMJ has published data that found that the estimated incidence of admission to hospital with confirmed Covid infection in pregnancy was 4.9 per 1,000 maternities.
Underlying health conditions seem to increase the risk of developing severe Covid for pregnant women. Among women who were pregnant on 5 March 2014 12.9% were at risk due to underlying health conditions. In 2020, a third of the pregnant women admitted to hospital with Covid had an underlying health condition.
The study also found that 12 (5%) of 265 infants tested positive for Sars-CoV-2 RNA, six of them within the first 12 hours after birth.
Men are more likely to suffer severe Covid, including hospitalisation and ICU admission, with those aged over 50 tending to suffer the most acute symptoms of coronavirus.
The risk of dying among those diagnosed with Covid is also higher in males, with working-age males diagnosed with Covid twice as likely to die as females.
A higher proportion of women are at risk of catching Covid but the association varies with age: research suggests that men are more likely than women to be at risk from the age of 55 upwards.
Sufferers of long Covid, however, are both relatively young and overwhelmingly female: women who get long Covid outnumber men by as much as four to one. Some experts suggest that the overall proportion of female long Covid patients could be even higher, potentially standing at 70-80%.
The risk of dying from Covid is higher in Black, Asian and Minority Ethnic (BAME) groups than in white ethnic groups
This is the opposite of what was seen in pre-Covid times, when the mortality rates were lower in Asian and Black ethnic groups than white ethnic groups.
After accounting for the effects of sex, age, deprivation and region, people of Bangladeshi ethnicity were found to have about twice the risk of death than people of white British ethnicity.
People of Chinese, Indian, Pakistani, other Asian, Caribbean and other black ethnicity had a higher risk of death, of between 10% and 50%, compared with white British individuals.
These analyses do not account for the effect of occupation, comorbidities or obesity.
The latest Oxford OpenSafely data show that vaccination rates in black communities are consistently 20 percentage points below the vaccination rates for the white community. For the 80+ age group vaccination coverage has been about 75% for black people and about 95% for white people.