The Friday Report – Issue 19
By Matt Fletcher, Nicola Oliver and John Roberts
COVID-19 Actuaries Response Group – Learn. Share. Educate. Influence.
COVID-19 is still one of the hottest topics for scientific papers and articles. The COVID‑19 Actuaries Response Group will provide you with a regular Friday update with a curated list of the key papers and articles that we’ve looked at recently.
Modelling – reports
A mathematical model reveals the influence of population heterogeneity on herd immunity to SARS‑CoV-2 (link)
Early in the pandemic, the models used suggested that (unvaccinated) herd immunity to SARS-CoV-2 would not be reached until around 60-70% of the population had been infected. This paper suggests that, due to heterogeneity in age and activity, the true figure could be around 40% – whilst considerably lower than previous estimates, this is some way above the estimated proportions infected in even the worst affected areas.
Assessing the age specificity of infection fatality rates for COVID-19: systematic review, meta-analysis, and public policy implications (link)
This pre-print is a systematic review of infection fatality rate (IFR) studies – it looks at the IFR for COVID-19 in different age bands across various types of study in multiple countries. Its conclusion is that COVID-19 poses a risk even for healthy middle-aged adults, with an IFR of 0.3% for ages 50-59, 1.3% for ages 60-69, 4% for ages 70-79 and 10% for ages 80-89.
Comparison of molecular testing strategies for COVID-19 control: a mathematical modelling study (Imperial College COVID-19 Response Team) (link)
This paper uses a mathematical model to estimate the impact of different strategies on testing and isolating symptomatic individuals, on the transmission of SARS-CoV-2. The effectiveness of these strategies is expressed in terms of the reduction in the effective reproduction number R that results.
The analysis suggests that if all individuals with symptoms self-isolated, and if that self-isolation was 100% effective in reducing transmission, R would only reduce by around 50%, with weekly screening of healthcare workers potentially reducing their contribution to transmission by a further 23%, and effective track and trace (involving immediate testing and quarantine of contacts within 24 hours) by 26%. The authors conclude that, although molecular testing can be important in preventing transmission of SARS‑CoV-2, there is no single strategy that can bring R below 1 based on current levels of population immunity.
Clinical and Medical News
Association of Race With Mortality Among Patients Hospitalized With COVID-19
This study (link) was conducted in order to further our understanding of the association between race and mortality in people with COVID-19. So far, it has been observed that people from a BAME background are disproportionately affected by COVID-19. Deaths during hospitalization of 11,210 US adult patients with COVID-19 were studied. The analysis was adjusted for age, sex, insurance status, comorbidity, neighbourhood deprivation, and site of care.
In this study, no statistically significant difference by race was observed; higher risk of all-cause in-hospital mortality was associated with older age, male sex, Medicare insurance, coexisting chronic kidney disease, and coronary artery disease.
Hydroxychloroquine as Postexposure Prophylaxis for Covid-19
Hydroxychloroquine has been the subject of a number of clinical studies to investigate its effectiveness in treating COVID-19. Many of the studies have focused on hospitalised patients; in this study (link), the aim was to prevent symptomatic infection after SARS-CoV-2 exposure. 821 asymptomatic patients who had had household or occupational exposure to someone with confirmed COVID-19 at a distance of less than 6 feet for more than 10 minutes were enrolled. They were categorised as either high-risk exposure (wearing neither a face mask nor an eye shield), or moderate risk exposure (face mask but no eye shield).
Four days after exposure, participants were randomly assigned to receive either placebo or hydroxychloroquine. The primary outcome was the incidence of either laboratory-confirmed COVID-19 or illness compatible with COVID-19 within 14 days. The study reports that hydroxychloroquine did not demonstrate a significant benefit in terms of post-exposure prophylaxis in either of the exposure groups. The researchers suggest that there may yet be benefit in pre-exposure prophylaxis; trials are on-going.
Risk factors for positive and negative COVID-19 tests
Risk factors for COVID-19 are analysed in this study (link) which used SARS-CoV-2 infection test data (4509 tests of which 1325 were positive) from Public Health England, linked to the UK Biobank study. The contribution of demographic, social, health risk, medical and environmental factors to COVID-19 risk were examined.
Results from the full adjusted model suggest that male sex, Black ethnicity, social disadvantage, being a healthcare worker, unemployed or retired, a current or former smoker, severely obese, comorbidities (cancer, cardiovascular disease, respiratory or autoimmune diseases), and greater exposure to pollution were all independently associated with the risk of being tested for COVID-19. In addition, the researchers find that among tested individuals, male sex, non-White ethnicity and lower educational attainment were associated with testing positive.
Diabetes and COVID-19
People with diabetes are at higher risk of COVID-19-related mortality than people without diabetes. Recent analyses have added additional clarity and evidence to this.
The first, a whole-population study undertaken using data from the National Diabetes Audit (NDA) sought to assess the independent effects of diabetes status, by type, on in-hospital death in England in patients with COVID-19 during the period from March 1 to May 11, 2020 (link).
The associations between diabetes status, sex, age group, ethnicity, deprivation, region, and comorbidities and in-hospital death with COVID-19 were analysed. Following adjustment, people with diabetes were found to have up to three times the mortality risk; the highest risk was seen in those with type 1 diabetes.
The same team also examined the associations between risk factors and COVID-19-related mortality in people with type 1 and type 2 diabetes (link). Key risks included cardiovascular and renal complications, BMI and poor glycaemic control.
Tocilizumab, a monoclonal antibody directed against the interleukin-6 receptor, may be efficacious in mitigating the cytokine storm syndrome associated with severe COVID-19. Use of this drug in severely ill COVID-19 patients admitted to ICU has been tested and early results look promising (link).
Patients from 13 hospitals in the US were included in the analysis (n = 764), of whom, 210 received tocilizumab. A reduction in hospital-related mortality was reported in those patients with COVID-19 requiring ICU support who received tocilizumab, (HR 0·64, 95% CI 0·47–0·87; p=0·0040). (However, do note that this was a retrospective observational cohort study, an approach that may have some methodological weaknesses.)
The ONS continues to publish regular bulletins relating to the pandemic, with updates this week on infectivity levels within different segments of the community, together with a survey on how COVID‑19 has affected levels of depression.
The infectivity survey (link) was carried out between 8th June and 2nd August, and sampled 51,000 lives of whom 67 were positive. With much lower numbers of infections, subdivisions are yielding little firm insight due to wide confidence intervals, although with regard to ethnicity, the Asian community is highlighted as having a notably higher prevalence. The survey also reports on antibody testing, with the overall level still running at between 5% and 6%.
It was also announced on Wednesday that sampling is going to be dramatically increased, to around 150,000 a fortnight, with the aim of spotting local hotspots much quicker than at present.
The survey on depression (link) was conducted in June and notes that overall there has been a marked increase in levels of depression, from 10% to 19%. The most notable increase has been in younger (18 to 39) adults, up from 11% to 31%. Females, those with disabilities, and those struggling financially have also been proportionally more affected in terms of their mental health.
T-cell response to SARS-CoV-2
There have been a number of papers written about T-cell responses to SARS-CoV-2 in unexposed individuals – for example link 1 and more recently link 2. This has led to hopes and claims that pre-existing T-cell immunity may mean that populations can reach herd immunity with only 10-20% infection.
One of the authors of the linked papers has recently written a helpful and widely-shared Twitter thread (link) explaining that, whilst it is conceivable that pre-existing T-cell immunity could help to reduce COVID-19 disease severity, it won’t limit the number of COVID-19 infections and hence actions to limit the disease’s spread are still vitally important.
US Study on the impact of 1m deaths.
A research article (link) published by the National Academy of Sciences of the United States of America considers the impact on life expectancy in the event of 1m deaths from COVID-19 in the USA (population c 330m). It suggests that life expectancy for 2020 would fall by 2.9 years, and those dying would lose an average of 11.7 years of life.
Even at that level, around five times current excess deaths in the US, the impact would be less than that of the Spanish Flu, but comparable with the impact of opioid or HIV deaths, albeit compressed into a much shorter timescale.
And finally …
If you’re stuck for ideas on what to do if you find yourself subject to quarantine rules, how about a game of ‘Surviving Quarantine’? The game was invented by a family of six in the US and the rules are simple: avoid the viruses, use vaccines, antidote and other cards to protect yourself from other players and survive another round. Cards include unicorn viruses, vaccines and antidotes made from chewing gum and cheese.
The supreme trump card is a laser shark … laser sharks and unicorns
21 August 2020