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Juan Lama
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COVID-19 has already had a staggering impact on the world up to the beginning of the omicron (B.1.1.529) wave, with over 40% of the global population infected at least once by Nov 14, 2021. The vast differences in cumulative proportion of the population infected across locations could help policy makers identify the transmission-prevention strategies that have been most effective, as well as the populations at greatest risk for future infection. This information might also be useful for targeted transmission-prevention interventions, including vaccine prioritisation. Background Timely, accurate, and comprehensive estimates of SARS-CoV-2 daily infection rates, cumulative infections, the proportion of the population that has been infected at least once, and the effective reproductive number (Reffective) are essential for understanding the determinants of past infection, current transmission patterns, and a population's susceptibility to future infection with the same variant. Although several studies have estimated cumulative SARS-CoV-2 infections in select locations at specific points in time, all of these analyses have relied on biased data inputs that were not adequately corrected for. In this study, we aimed to provide a novel approach to estimating past SARS-CoV-2 daily infections, cumulative infections, and the proportion of the population infected, for 190 countries and territories from the start of the pandemic to Nov 14, 2021. This approach combines data from reported cases, reported deaths, excess deaths attributable to COVID-19, hospitalisations, and seroprevalence surveys to produce more robust estimates that minimise constituent biases. Methods We produced a comprehensive set of global and location-specific estimates of daily and cumulative SARS-CoV-2 infections through Nov 14, 2021, using data largely from Johns Hopkins University (Baltimore, MD, USA) and national databases for reported cases, hospital admissions, and reported deaths, as well as seroprevalence surveys identified through previous reviews, SeroTracker, and governmental organisations. We corrected these data for known biases such as lags in reporting, accounted for under-reporting of deaths by use of a statistical model of the proportion of excess mortality attributable to SARS-CoV-2, and adjusted seroprevalence surveys for waning antibody sensitivity, vaccinations, and reinfection from SARS-CoV-2 escape variants. We then created an empirical database of infection–detection ratios (IDRs), infection–hospitalisation ratios (IHRs), and infection–fatality ratios (IFRs). To estimate a complete time series for each location, we developed statistical models to predict the IDR, IHR, and IFR by location and day, testing a set of predictors justified through published systematic reviews. Next, we combined three series of estimates of daily infections (cases divided by IDR, hospitalisations divided by IHR, and deaths divided by IFR), into a more robust estimate of daily infections. We then used daily infections to estimate cumulative infections and the cumulative proportion of the population with one or more infections, and we then calculated posterior estimates of cumulative IDR, IHR, and IFR using cumulative infections and the corrected data on reported cases, hospitalisations, and deaths. Finally, we converted daily infections into a historical time series of Reffective by location and day based on assumptions of duration from infection to infectiousness and time an individual spent being infectious. For each of these quantities, we estimated a distribution based on an ensemble framework that captured uncertainty in data sources, model design, and parameter assumptions. Findings Global daily SARS-CoV-2 infections fluctuated between 3 million and 17 million new infections per day between April, 2020, and October, 2021, peaking in mid-April, 2021, primarily as a result of surges in India. Between the start of the pandemic and Nov 14, 2021, there were an estimated 3·80 billion (95% uncertainty interval 3·44–4·08) total SARS-CoV-2 infections and reinfections combined, and an estimated 3·39 billion (3·08–3·63) individuals, or 43·9% (39·9–46·9) of the global population, had been infected one or more times. 1·34 billion (1·20–1·49) of these infections occurred in south Asia, the highest among the seven super-regions, although the sub-Saharan Africa super-region had the highest infection rate (79·3 per 100 population [69·0–86·4]). The high-income super-region had the fewest infections (239 million [226–252]), and southeast Asia, east Asia, and Oceania had the lowest infection rate (13·0 per 100 population [8·4–17·7]). The cumulative proportion of the population ever infected varied greatly between countries and territories, with rates higher than 70% in 40 countries and lower than 20% in 39 countries. There was no discernible relationship between Reffective and total immunity, and even at total immunity levels of 80%, we observed no indication of an abrupt drop in Reffective, indicating that there is not a clear herd immunity threshold observed in the data. Published in The Lancet (April 8, 2022):
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Scooped by
Juan Lama
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Nations short of vaccine should get first doses to curb the pandemic, researchers say. Israel has announced plans to begin giving booster shots to older adults next week, in the hope of increasing their protection against COVID-19 — and a number of other wealthy countries are considering the same. But global-health researchers warn that this strategy could set back efforts to end the pandemic. Each booster, they say, represents a vaccine dose that could instead go to low- and middle-income countries, where most citizens have no protection at all, and where dangerous coronavirus variants could emerge as cases surge. Data do not yet show that extra doses are needed to save lives, researchers say, except perhaps for people with compromised immune systems, who might fail to generate much of an antibody response to the initial COVID-19 shots. An internal analysis from the World Health Organization (WHO) estimates that if the 11 rich countries that are either rolling out boosters or considering it this year were to give the shots to everyone over 50 years old, they would use up roughly 440 million doses of the global supply. If all high-income and upper-middle-income nations were to do the same, the estimate doubles. The WHO maintains that these shots would be more useful for curbing the pandemic if they were sent to low- and lower-middle-income countries, where more than 85% of people — some 3.5 billion — haven’t had a single jab. “The priority now must be to vaccinate those who have received no doses,” said WHO director-general Tedros Adhanom Ghebreyesus at a briefing on 12 July. All of the COVID-19 vaccines authorized by most high-income countries reduce a person’s risk of hospitalization and death by more than 90%. Scientists don’t yet know how much more a booster — typically an extra jab of an mRNA-based vaccine on top of the standard doses — would protect the average person, although data are beginning to trickle in. The effects of not receiving any vaccine are more certain. On the African continent, where only 2% of people have been vaccinated, COVID-19 rates are escalating, with fatality rates higher than the global average. Without vaccines, researchers say, the best tools for slowing the spread of infections are interventions such as closing businesses and schools, which can have devastating economic consequences. The International Monetary Fund (IMF) estimates that 95 million people were pushed into extreme poverty during the pandemic last year, and numbers are rising. On 27 July, the organization reported a widening wealth gap between rich countries and the rest of the world. What’s more, evolutionary biologists say that countries with low vaccination coverage are ripe for the emergence of further dangerous variants of the coronavirus SARS-CoV-2. “Right now, our destiny relies on distributing vaccines so that continued transmission doesn’t occur,” says Nahid Bhadelia, director of the Center for Emerging Infectious Diseases Policy and Research at Boston University in Massachusetts. “We don’t want to be chasing our tail in terms of new variants.” Contemplating boosters Israel is not alone in considering boosters for older people. Spurred partly by data1 suggesting that antibody levels wane over time, the United Kingdom has drawn up plans — but not given final approval — for a booster programme to begin in September for older people, front-line health workers and others at high risk of COVID-19. In early July, the US government decided against boosters for the time being, but said it was prepared to roll them out when science demonstrated a need. Last week, the United States purchased another 200 million mRNA vaccines made by pharmaceutical firm Pfizer, based in New York City, and biotechnology firm BioNTech, based in Mainz, Germany, that might be used for booster shots if studies show they are necessary. The United States and other nations are hesitating because current COVID-19 vaccines still protect people, despite uncertainty about how long their effects will last. This week, a not-yet peer-reviewed report from Pfizer2 found that its vaccine’s efficacy rate against symptomatic COVID-19 fell from 96% for the two months after the usual two doses to 84% six months later. But its efficacy against severe disease remained high, at 97%. Decisions on boosters might also be influenced by the rise of the Delta variant in many parts of the world, and the possibility that vaccinated people could transmit it to others if they become infected. In theory, further reducing the risk of infection for vaccinated people diminishes the possibility of Delta's spread. The variant was first reported in India in late 2020, but remained relatively rare until March, when a surge occurred. Few people in the country had been vaccinated at the time, allowing the virus to spread in India and beyond. A similar scenario might play out again in an area with low vaccination coverage and a lot of COVID-19. A new variant could arise that is more transmissible or deadlier than Delta, or that allows the virus to escape — at least to some extent — immunity gained from vaccination or a previous infection, says Katrina Lythgoe, an evolutionary biologist at the Big Data Institute at the University of Oxford, UK. “Making predictions is really hard,” she adds, but it’s safe to say that in places with more infections, there are more viruses replicating and therefore more opportunities for variants to evolve....
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Scooped by
Juan Lama
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Vaccines have slowed the death rate, but officials warn of worrying rises in some countries. The milestone comes amid warnings from health officials that cases and deaths in some places are rising for the first time in months. Nearly 250 million cases of the virus have been recorded worldwide. The World Health Organization (WHO) estimates the pandemic's real global death toll could be two to three times higher than official records. In the US, more than 745,800 people have died, making it the country with the highest number of recorded deaths. It is followed by Brazil, with 607,824 recorded deaths, and India, with 458,437. But health experts believe these numbers are under reported, partly because of deaths at home and those in rural communities. It has taken the world longer to reach the latest one million deaths than the previous two. It took over 110 days to go from four million deaths to five million. That is compared to just under 90 days to rise from three million to four million. While vaccines have helped reduce the fatality rate, the WHO warned last week that the pandemic was "far from over". Its director general Tedros Adhanom Ghebreyesus pointed to a rise in cases in Europe, where countries with low vaccination rates are seeing soaring infections and deaths. Last week, Russia recorded its highest number of daily cases and deaths since the start of the pandemic. Russia accounts for 10% of the last million deaths recorded globally. Bulgaria and Romania have some of the world's worst Covid mortality rates, and their hospitals are struggling to cope. They have the two lowest vaccine rates in the European Union. More than seven billion vaccine doses have been administered worldwide, but there is a gap between rich and poor nations. Only 3.6% of people in low income countries have been vaccinated, according to Oxford University's Our World in Data. Dr Tedros said that if the vaccine doses had been distributed fairly, "we would have reached our 40% target in every country by now". "The pandemic persists in large part because inequitable access to tools persists," he said. Vaccines have allowed many countries to gradually open up, with most of the world now easing restrictions. On Monday, Australia reopened its borders for the first time in 19 months. But China, where the pandemic first emerged, is still perusing a zero-Covid strategy, where even one infection can result in a strict lockdown and mass testing. A country's death toll is based on daily reports from the nation's health authorities, but the numbers may not fully reflect the true toll in many countries. Not all countries record coronavirus deaths in the same way, meaning it is difficult to compare their death rates. Comparing how different countries have suffered during the Covid pandemic is difficult. Total number of deaths is one way, but this number masks some crucial context. How much testing individual countries carry out will have a bearing on their death figures. Very few deaths have occurred in Africa, for example, compared to other continents and this is likely to be one factor. Deaths from Covid can also be measured in different ways - as a proportion of the population (Bulgaria fares worst) or as a proportion of people showing symptoms (Mexico fares worst). And the healthcare systems in different countries as well as the average age of the population will also have an impact - the older the people the more vulnerable they are to the virus. Vaccinations against Covid have made a huge difference to the number of people dying in the past six months - but not all countries have had equal access to shots which protect against the virus. That means there will be more deaths to come - but Covid is not the only health problem the world has to worry about. It's worth remembering that each year more than nine million people die from cancer and nearly the same number from heart disease.
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