Impact of the population age, testing and vaccination levels on the numbers of COVID-19 cases and deaths per capita and case fatality risks (preprint)

The population, governments and researchers show much less interest in the COVID-19 pandemic. However, many questions still need to be answered: why the much less vaccinated African continent has accumulated 15 times less deaths per capita than Europe? or why in 2023 the global value of the case fatality risk is almost twice higher than in 2022 and the UK figure is four times higher than the global one? The averaged daily numbers of cases DCC and death DDC per million, case fatality risks DDC/DCC were calculated for 34 countries and regions with the use of John Hopkins University (JHU) datasets and possible linear and non-linear correlations with the averaged daily numbers of tests per thousand DTC, median age of population A, and percentages of vaccinations VC and boosters BC were investigated. Strong correlations between age and DCC and DDC values were revealed. One-year increment in the median age yielded 39.8 increase in DCC values and 0.0799 DDC increase in 2022 (in 2023 these figures are 5.8 and 0.0263, respectively). With decreasing of testing level DTC, the case fatality risk can increase drastically. DCC and DDC values increase with increasing the percentages of fully vaccinated people and boosters, which definitely increase for greater A. After removing the influence of age, no correlations between vaccinations and DCC and DDC values were revealed. The presented analysis demonstrates that age is a pivot factor of visible (registered) part of the COVID-19 pandemic dynamics. Much younger Africa has registered less numbers of cases and death per capita due to many unregistered asymptomatic patients. Of great concern is the fact that COVID-19 mortality in 2023 in the UK is still at least 4 times higher than the global value caused by seasonal flu.

Population age as a key factor in the COVID-19 pandemic dynamics (preprint)

The population and governments of many countries are losing interest in the SARS-CoV-2 infection, the number of tests and the number of new cases detected is sharply decreasing. To compare the accumulated numbers CC of cases and deaths DC per million and to answer the question why the less vaccinated Africa has accumulated 36 times lower CC values and 15 times lower DC values than Europe, simple statistical analysis have been performed. CC and DC values demonstrated rather strong correlation with the median age of populations. One-year increment in the median year yields 12-18 thousand increase in CC values and 52-83 increase in DC values. Zero-COVID countries succeed to have much lower numbers of deaths per capita and case fatality ratios DC/CC.

Can we start to ignore the SARS-CoV-2 disease? (preprint)

Current WHO reports claim a decline in COVID-19 testing. Many countries are reporting no new infections. In particular, USA, China and Japan have registered no cases and COVID-19 related deaths since May 15, 2023. To discuss consequences of ignoring SARS-CoV-2 infection, we compare endemic characteristics of the disease in 2023 with ones estimated before using 2022 datasets. The accumulated numbers of cases and deaths reported to WHO by 10 most infected countries and global figures were used to calculate the average daily numbers of cases and deaths per capita (DCC and DDC) and case fatality rates (CFR) for two periods in 2023. The average values of daily deaths per million still vary between 0.12 and 0.41. It means that annual global number of COVID-19 related deaths is still approximately twice higher than the seasonal influenza mortality. Increase of CFR values in 2023 show that SARS-CoV-2 infection is still dangerous despite of increasing the vaccination level. Very low CFR figures in South Korea and very high ones in the UK 4 need further investigations.

The COVID-19 pandemic waves: comparative and statistical analysis of their dynamics (preprint)

Objective. Record numbers of new COVID-19 cases and deaths registered in Japan and European countries in early 2022 aroused new questions about methods of overcoming the pandemic. The pandemic waves in Japan, Ukraine, USA, and Hong Kong in 2020, 2021, 2022 will be compared. Possible influence of testing and vaccination levels will be investigated.Methods. The smoothed daily numbers of new cases and deaths per capita, the ratio of these characteristics and the non-linear correlation with the tests per case ratio were used.Results. As in other countries, the deaths per case ratio in Japan decreases with the increase of the vaccination level despite increasing daily numbers cases and deaths.Conclusions Non-linear correlation revealed, that the daily number of new cases drastically decreases with the increase of the tests per case ratio.Implications for Public Health. Increasing the level of testing and adhering to quarantine restrictions for the entire population, including vaccinated people, can be recommended to reduce the negative consequences of the COVID-19 pandemic.

Estimations of SARS-CoV-2 endemic characteristics (preprint)

The fourth year of the COVID-19 pandemic without decreasing trends in the global numbers of new daily cases, high numbers of circulating SARS-CoV-2 variants and re-infections together with pessimistic predictions for the Omicron wave duration force studies about the endemic stage of the disease. The global trends were illustrated with the use the accumulated numbers of laboratory confirmed COVID-19 cases and deaths, the percentages of fully vaccinated people and boosters and the results of calculation of the effective reproduction number provided by Johns Hopkins University. The modified SIR model showed the presence of unsteady equilibrium. The global numbers of new daily cases will range between 300 thousand and one million, daily deaths between one and 3.3 thousand.

Vaccination and testing as a means of ending the COVID-19 pandemic: comparative and statistical analysis (preprint)

ABSTRACT Background Record numbers of new cases and deaths registered in Japan and European countries in early 2022 once again proved that existing vaccines cannot stop the new infections and deaths caused by SARS-CoV-2 and aroused new questions about methods of overcoming the pandemic. Aim of the study to compare the pandemic waves in Japan, Ukraine, USA, Hong Kong, mainland China, European and African countries in 2020, 2021, 2022 and to investigate the influence of testing and vaccination levels. Methods The smoothed daily numbers of new cases and deaths per capita, the ratio of these characteristics and the non-linear correlation with the tests per case ratio were used. Results As in other countries, the deaths per case ratio in Japan decreases with the increase of the vaccination level. Non-linear correlation revealed, that the daily number of new cases drastically decreases with the increase of the tests per case ratio. Conclusions Increasing the level of testing (especially for people who may have contact with infected persons) and adhering to quarantine restrictions for the entire population, including vaccinated people, may be recommended to end the pandemic.

Coronavirus and incomes: the COVID-19 pandemic dynamics in Africa in February 2022 (preprint)

The relative accumulated and daily characteristics of the COVID-19 pandemic dynamics in Africa were used to find links with the gross domestic product per capita (GDP), percentages of fully vaccinated people and daily numbers of tests per case. A simple statistical analysis of datasets corresponding to February 1, 2022 showed that accumulated and daily numbers of cases per capita, daily numbers of deaths per capita and vaccination levels increase with the increase of GDP. As in the case of Europe, the smoothed daily numbers of new cases per capita in Africa increase with the increasing of the vaccination level. But the increase of the accumulated numbers of cases and daily number of deaths with increasing the vaccination level was revealed in Africa. In comparison with Europe, no significant correlation was revealed between the vaccination level and the number of deaths per case. As in the case of Europe, African countries demonstrate no statistically significant links between the pandemic dynamics characteristics and the daily number of tests per case. It looks that countries with very small GDP are less affected by the COVID-19 pandemic. The cause of this phenomenon requires further research, but it is possible that low incomes limit the mobility of the population and reduce the number of contacts with infected people. In order to overcome the pandemic, quarantine measures and social distance should not be neglected (this also applies to countries with a high level of income and vaccination).

Impact of the Russian invasion of Ukraine onthe COVID-19 pandemic dynamics (preprint)

Full-scale invasion of Ukraine by Russian troops, which began on February 24, 2022, caused an unprecedented number of refugees, which in the ongoing COVID-19 pandemic could increase the number of patients. The recent pandemic dynamics in Ukraine, Poland, Germany and in the whole world was compared with the previous epidemic waves simulated with the use of the generalized SIR-model and corresponding parameter identification procedure. Since before the war the estimation of the number of infectious persons per capita in Ukraine 3.6 times exceeded the global figure, the increase of the number the new cases and the pandemic duration is expected. From the beginning of March 2022 the increase of the averaged number of new cases in Germany and worldwide is visible.

How dangerous is omicron and how effective are vaccinations? (preprint)

The sharp increase in the number of new COVID-19 cases in late 2021 and early 2022, which is associated with the spread of a new strain of coronavirus - omicron - is of great concern and makes it necessary to make at least approximate forecasts for the pandemic dynamics of the epidemic. As this rapid growth occurs even in countries with high levels of vaccinations, the question arises as to their effectiveness. The smoothed daily number of new cases and deaths per capita and the ratio of these characteristics were used to reveal the appearance of new coronavirus strains and to estimate the effectiveness of quarantine, testing and vaccination. The third year of the pandemic allowed us to compare the pandemic dynamics in the period from September 2020 to January 2021 with the same period one year later for Ukraine, EU, the UK, USA, India, Brazil, South Africa, Argentina, Australia, and in the whole world. Record numbers of new cases registered in late 2021 and early 2022 once again proved that existing vaccines cannot prevent new infections, and vaccinated people can spread the infection as intensively as non-vaccinated ones. Fortunately, the daily number of new cases already diminishes in EU, the UK, USA, South Africa, and Australia. In late January - early February 2022,the maximum averaged numbers of new cases are expected in Brazil, India, EU, and worldwide. "Omicron" waves can increase the numbers of deaths per capita, but in highly vaccinated countries, the deaths per case ratio significantly decreases.

The impact of demographic factors on numbers of COVID-19 cases and deaths in Europe and the regions of Ukraine (preprint)

ABSTRACT The accumulated numbers of COVID-19 cases and deaths per capita are important characteristics of the pandemic dynamics that may also indicate the effectiveness of quarantine, testing, vaccination, and treatment. The statistical analysis based on the number of cases per capita accumulated to the end of June 2021 showed no correlations with the volume of population, its density, and the urbanization level both in European countries and regions of Ukraine. The same result was obtained with the use of fresher datasets (as of December 23, 2021). The number of deaths per capita and per case may depend on the urbanization level. For European countries these relative characteristics decrease with the increase of the urbanization level. Opposite trend was revealed for the number of deaths per capita in Ukrainian regions.

Final sizes and durations of new COVID-19 pandemic waves in Poland and Germany predicted by generalized SIR model (preprint)

New waves of the COVID-19 pandemic in Europe, which began in the autumn of 2021, are a matter of great concern and the need to immediately predict the epidemic dynamics in order to assess the possible maximum values of new cases, the risk of infection and the number of deaths. The generalized SIR-model and corresponding parameter identification procedure was used to simulate and predict the dynamics of new epidemic waves in Poland and Germany. Results of calculations show that new cases in these countries will not stop to appear in 2022.

Final sizes and durations of new COVID-19 pandemic waves in Ukraine and around the world predicted by generalized SIR model (preprint)

ABSTRACT New waves of the COVID-19 pandemic in Ukraine, which began in the summer of 2021, and after holidays in the middle of October 2021, were characterized by almost exponential growth of smoothed daily numbers of new cases. This is a matter of great concern and the need to immediately predict the epidemic dynamics in order to assess the possible maximum values of new cases, the risk of infection and the number of deaths. The generalized SIR-model and corresponding parameter identification procedure was used to simulate and predict the dynamics of two new epidemic waves in Ukraine and one in the whole world. Results of calculations show that new cases in Ukraine will not stop to appear before November 2022. If the global situation with vaccination, testing and treatment will not change, the pandemic could continue for another ten years.

Simulation and predictions of a new COVID-19 pandemic wave in Ukraine with the use of generalized SIR model (preprint)

A new wave of the COVID-19 pandemic in Ukraine, which began in the summer of 2021, was characterized by almost exponential growth of smoothed daily numbers of new cases. This is a matter of great concern and the need to immediately predict the dynamics of the epidemic in order to assess the possible maximum values of new cases, the risk of infection and the number of deaths. The generalized SIR-model and corresponding parameter identification procedure was used to simulate and predict the dynamics of this epidemic wave. The new COVID-19 epidemic wave in Ukraine will begin to subside in mid-October 2021, but its duration will be quite long. Unfortunately, new cases may appear by the summer of 2022.

Effects of testing and vaccination levels on the dynamics of the COVID-19 pandemic and the prospects for its termination (preprint)

ABSTRACT A simple statistical analysis of the accumulated and daily numbers of new COVID-19 cases and deaths per capita was performed with the use of recent datasets for European and some other countries and regions. It was shown that vaccination can significantly reduce the likelihood of deaths. However, existing vaccines do not prevent new infections, and vaccinated individuals can spread the infection as intensely as unvaccinated ones. Therefore, it is too early to lift quarantine restrictions in Europe and most other countries. The constant appearance of new cases due to re-infection increases the likelihood of new coronavirus strains, including very dangerous. As existing vaccines are not able to prevent this, it remains to increase the number of tests per registered case. If the critical value of 520 is exceeded, one can hope to stop the occurrence of new cases.

The impact of seasonal factors on the COVID-19 pandemic waves (preprint)

The daily number of new COVID-19 cases per capita is an important characteristic of the pandemic dynamics indicating the appearance of new waves (e.g., caused by new coronavirus strains) and indicate the effectiveness of quarantine, testing and vaccination. Since this characteristic is very random and demonstrates some weekly period, we will use the 7-days smoothing. The second year of the pandemic allows us to compare its dynamics in the spring and the summer of 2020 with the same period in 2021 and investigate the influence of seasonal factors. We have chosen some northern countries and regions: Ukraine, EU, the UK, USA and some countries located in tropical zone and south semi-sphere: India, Brazil, South Africa and Argentina. The dynamics in these regions was compared with COVID-19 pandemic dynamics in the whole world. Some seasonal similarities are visible only for EU and South Africa. In 2020, the southern countries demonstrated the exponential growth, but northern regions showed some stabilization trends.

Will a natural collective immunity of Ukrainians restrain new COVID-19 waves? (preprint)

The visible and real sizes the COVID-19 epidemic in Ukraine were estimated with the use of the number of laboratory-confirmed cases (accumulated in May and June 2021), the generalized SIR-model and the parameter identification procedure taking into account the difference between registered and real number of cases. The calculated optimal value of the visibility coefficient shows that most Ukrainians have already been infected with the coronavirus, and some more than once, i.e., Ukrainians have probably achieved a natural collective immunity. Nevertheless, a large number of new strains and short-lived antibodies can cause new pandemic waves. In particular, the beginning of such a wave, we probably see in Ukraine in mid-July 2021. The further dynamics of the epidemic and its comparison with the results of mathematical modeling will be able to answer many important questions about the natural immunity and effectiveness of vaccines.

The impact of demographic factors on the accumulated number of COVID-19 cases per capita in Europe and the regions of Ukraine in the summer of 2021 (preprint)

The accumulated number of COVID-19 cases per capita is an important characteristic of the pandemic dynamics that may also indicate the effectiveness of quarantine, testing and vaccination. As this value increases monotonically over time, the end of June 2021 was chosen, when the growth rate in Ukraine and the vast majority of European countries was small. This allowed us to draw some intermediate conclusions about the influence of the volume of population, its density, and the level of urbanization on the accumulated number of laboratory-confirmed cases per capita in European countries and regions of Ukraine. A simple analysis showed that the number of cases per capita does not depend on these demographic factors, although it may differ by about 4 times for different regions of Ukraine and more than 9 times for different European countries. The number of COVID-19 per capita registered in Ukraine is comparable with the same characteristic in other European countries but much higher than in China, South Korea and Japan.

Forecast verifications for the real COVID-19 pandemic dynamics in Qatar (preprint)

ABSTRACT The COVID-19 pandemic dynamics in Qatar in the second half of May and the first half of June 2021 was compared with the published results of SIR-simulations based on the data from the period April 25 - May 8, 2021. Forecast verification showed very good agreement with the real number of cases (which can exceed the laboratory-confirmed one more than 5 times). The positive effect of mass vaccination became visible in June 2021.

Visible and real dynamics of the COVID-19 pandemic in Ukraine in the spring of 2021 (preprint)

The visible and real sizes the last COVID-19 epidemic wave in Ukraine, estimated in March 2021 with the use of generalized SIR-model, are compared with number of cases registered in the spring of 2021. We have used the optimal value of the visibility coefficient in order to estimate the real numbers of accumulated cases, real daily numbers of new cases and real number of infectious persons. The results show that the latest prediction for Ukraine is in rather good agreement with observations, but the daily number of new cases decreases more slowly than theoretical predictions. The large real number of infectious people threatens the emergence of new strains of coronavirus and the beginning of new epidemic waves.

The COVID-19 pandemic storm in India subsides, but the calm is still far away (preprint)

ABSTRACT In May 2021, the number of new COVID-19 patients in India began to decline, as predicted by the generalized SIR-model (susceptible-infected-removed). The calculations of the final size of this pandemic wave and its duration probably were too pessimistic. New SIR simulations with the use of fresher datasets are necessary in order to update the predictions and to calculate the difference between the registered (laboratory-confirmed) and real number of cases.