And rapid antigen tests may be losing their sensitivity as population immunity increases.
Your weekly pandemic wrap from Australia and around the world.
9 May
- The antiviral remdesivir has been provisionally approved for babies and young children, and anyone at risk of severe disease.
- RATs may be losing their sensitivity as vaccination increases immunity.
- Boosters increase protection against Omicron in nursing home residents.
- Covid in pregnancy increases risk of preterm birth, hospitalisation and ICU admission.
- Excess deaths in pandemic approached 15 million even before Omicron.
Remdesivir is now provisionally approved for use in covid patients as young as four weeks of age who have developed pneumonia due to SARS-CoV-2 infection and require oxygen.
The drug was originally approved for adults and adolescents aged 12 and over needing supplemental oxygen. As well as being extended to include babies aged over four weeks and weighing more than 3 kgs, it can also be used in those aged over 12 years who are not on supplemental oxygen but who are at high risk of progressing to severe disease.
Rapid antigen tests may be becoming less sensitive as population immunity increases, research suggests.
A non-peer-reviewed study, published on The Lancet’s preprint site, looked at the change in sensitivity of rapid antigen tests taken by 8300 symptomatic and 5,500 asymptomatic employees at three healthcare facilities between December 2020 and February 2022.
Using RT-PCR to confirm results, the study found that sensitivity of RATs – their ability to accurately detect positive cases – was around 80% until September 2021, then gradually dropped to around 67% by the end of February 2022.
However, the decline in sensitivity wasn’t due to viral load, as the average viral load in swabs actually increased slightly towards the end of the study period. Nor was there any laboratory evidence that the RATs were less sensitive to more recent variants including Omicron and Delta.
The authors did note that vaccination rates increased substantially. None of the participants who tested positive on RT-PCR in April/May 2021 were double-vaccinated or previously infected, but by January this year, around two-thirds of those in the study were triple-vaccinated.
They suggested that immunisation might be the reason for the apparent decline in RAT sensitivity over the study period.
“If immunized subjects have faster immune reactions, resulting in earlier symptoms, they will on average present for testing earlier in the course of infection,” they wrote.
This means RATs, which detect virus-infected cells bearing the viral N-protein, are being used sooner after infection, when the shedding of those N-protein-bearing cells may not yet have reached levels high enough for detection.
“The higher likelihood of early false negative results and resultant lack of power to exclude an infection by early AgRDT [antigen] testing must be borne in mind at all levels, from tests in individuals, to policies for institutions such as hospitals, and in more general consideration of overall pandemic response policy,” they wrote.
A booster dose increases protection against Omicron infection by nearly 47% among nursing home residents compared to a primary course of vaccine, a study has found.
A paper published in Morbidity and Mortality Weekly Report analysed data from around 15,000 nursing homes across the United States to understand the link between infection rates among residents and their vaccination status in the first months of this year.
Overall, nearly two-thirds of residents had received their first booster dose, and more than 90% of these were mRNA vaccines.
The study found the booster dose was associated with significantly greater protection than two doses alone, although it didn’t include data on severity of illness.
SARS-CoV-2 infection during pregnancy is associated with a significant increase in the risk of preterm birth, even in people with mild infection, according to a paper published in JAMA.
A study of just over 6000 pregnant people with laboratory-confirmed covid in Canada, before widespread vaccination was available, found a 60% higher rate of preterm birth among those with SARS-CoV-2 – including mild cases of infection – compared to the rate in a non-covid-affected general population. Just under half the preterm births were spontaneous, and just over half were induced.
Researchers also found pregnant people with covid had a 2.6-times greater risk of hospitalisation and five times greater risk of ICU admission compared to non-pregnant females with SARS-CoV-2 infection.
Older age, hypertension, BMI, diabetes, asthma and ethnicity were all associated with an increased risk of worse maternal outcomes, but among the few people who were double-vaccinated, none experienced adverse outcomes.
Nearly 15 million excess deaths have occurred globally over the course of the pandemic, yet only six million official covid deaths have been reported.
The World Health Organisation has released a report on global excess deaths – defined as the difference between the total number of deaths that have occurred and the number of deaths that were expected to happen if covid had not shown up – which found 14.91 million more people died between January 2020 and December 2021 than was expected based on historical trends.
Given the data set ends just before the Omicron peak, that figure is likely to be an underestimate.
However excess deaths were not distributed equally around the world, with 80% of excess deaths occurring in 20 countries that contain around 50% of the global population, including the US, UK, Germany, India, Indonesia and Russia.
They also weren’t distributed equally by income, with the greatest discrepancies between reported covid deaths and excess deaths seen in low and middle-income countries.
Australia shows consistently negative excess deaths, meaning that fewer people died than would have been expected, which may be the result of declines in deaths from other causes including chronic respiratory disease and influenza. However, that may change with the recent Omicron peak, which has significantly increased the death rate from covid.
Meanwhile, new covid infections globally have fallen a further 17% in the past week, along with a 3% drop in deaths, according to the latest WHO figures.
Omicron continues to generate new subvariants – BA.4, BA.5 and BA.2.12.1 are the latest – all of which have mutations that could affect their behaviour. WHO says that while the subvariants do appear to have a growth advantage over earlier variants, there is no evidence yet to suggest that they are more severe.
