A recent study conducted by Harvard University in America has put forward a number of scenarios predicting the behavior of the virus over the next few years. It reveals that the virus has become permanent and that COVID-19 will become seasonal.
Nearly four months after the first case of COVID-19 was reported in Wuhan, China, the world is still reeling from the shock of the pandemic, which has infected more than 3.5 million people and claimed over a quarter of a million lives. According to Johns Hopkins University, the Middle East has recorded more than 8,800 deaths worldwide. Shockingly, half of these deaths occurred in just the previous 16 days, according to figures released on April 25.
Nearly a month and a half after the World Health Organization declared the novel coronavirus a global pandemic, many countries imposed complete lockdowns on their citizens to maintain social distancing measures as a crucial step to curb the spread of the virus and alleviate pressure on the healthcare sector. But the question remains, and everyone is eager to know the answer: When will life return to normal?
This is what Steven Kessler, a postdoctoral researcher in immunology and infectious diseases at the Harvard School of Public Health, and his colleagues attempted to answer by building a simulation model that predicts the virus’s behavior over the next few years. They published their model’s findings in a recent study in the journal Science last April. The results showed that the total number of COVID-19 infections up to 2025 will depend critically on the development of human immunity. The Harvard team’s computer simulation assumed that COVID-19 will become seasonal, like other coronaviruses that cause the common cold, with transmission rates increasing in the colder months. This comes at a time when researchers still lack much information about the virus, including the level of immunity acquired from previous infection. The study’s findings underscore one near certainty: the virus is here to stay, and it is unlikely that humanity will develop strong, long-lasting immunity to eradicate COVID-19 after the first wave, as happened with SARS in 2002-2003.
Economic and social burdens
The study authors point out that while a one-time implementation of social distancing may reduce critical cases and alleviate the burden on the healthcare sector, infections will resurface once these measures are lifted. Without new treatments or an effective vaccine, or without other measures such as thorough contact tracing, testing, and quarantine when necessary, social distancing may need to be maintained, even intermittently, until 2022, posing a significant social and economic burden. Extensive viral testing will be required to determine when social distancing measures should be reinstated.
“Allowing transmission periods that reach a higher prevalence rate is likely to accelerate the acquisition of herd immunity,” says co-author Mark Lipsick. Conversely, prolonged periods of social isolation without relief are detrimental. The study’s findings reveal that in one scenario, “social isolation was so effective that almost no immunity was built up in the community,” hence the need for a nuanced approach.
Many countries have taken numerous measures to try to control the spread of the virus, most notably conducting extensive testing to detect the virus and providing immediate care to infected individuals. Other countries have adopted measures such as closing schools, universities, and workplaces, and limiting gatherings. The main objective of these strategies is to reduce the peak of the virus’s spread, either by maintaining a stable level of infections or by causing a slight—albeit small—decline in their numbers, a process scientists call “flattening the curve.”
Islam Anan, CEO of Accsight Healthcare Research and a lecturer in health economics and epidemiology, explains that social distancing scenarios for the current pandemic are the only tool we have now to combat the spread of the virus, adding: “They must first be enforced by law through curfews, and then a strong awareness campaign should be launched about their importance.”
However, Annan makes an exception for countries adopting social distancing measures that will continue until 2022. He argues that if this were to happen, “it would mean increasing the budget allocated to healthcare, which is already low, as government spending on health represents only 2-5% of GDP in many developing countries.” He adds that another burden requiring a huge budget would be the development of new tools to help with social distancing, particularly in schools and on public transport.
What will happen after the pandemic ends?
To build a model of how the novel coronavirus might spread over the next five years, Kessler and his colleagues used available data in the United States on seasonal infections with similar coronaviruses and the levels of immunity the human body develops against them, called cross-immunity. This type of immunity arises when a person is infected with viruses similar to a particular virus, leading to the production of antibodies against it. Consequently, this person acquires partial immunity when a new virus with similar characteristics to the previous viruses emerges.
In this study, researchers developed five scenarios regarding the impact of a one-time social distancing measure on virus transmission, taking into account several variables, such as whether the virus is seasonal, the healthcare system’s capacity to handle critical cases, and the development and timing of herd immunity. They also assumed that each infected person would transmit the virus to 2.2 others, scientifically known as R0 = 2.2. These scenarios were developed for varying time periods: four weeks, eight weeks, twelve weeks, twenty weeks, and a final scenario involving indefinite social distancing.
Herd immunity is the immunity that a large number of people in a community acquire against a particular infection, which limits its spread. It is formed through previous infection with the disease, or through the development of a vaccine against it, and by immunizing as many people as possible with it.
The study showed that when disease transmission is not subject to seasonal factors, a single instance of social distancing measures reduces the spread of the epidemic. All scenarios also indicated a resurgence of infections once these measures were lifted. Therefore, the study’s findings suggest that if seasonal transmission proves to be the norm, we will need to implement social distancing with each new wave of the virus and double our capacity to care for critical cases within healthcare systems to be prepared for future waves. The study clarified that herd immunity is a key pillar for eradicating the pandemic, but the virus could return in a new wave within 4 to 5 years. If cross-immunity develops with other similar coronaviruses, it will also lead to herd immunity, thus eradicating the pandemic and resulting in fewer future waves.
The study’s model was consistent with other models of how the novel coronavirus spreads. Another model, using data from Sweden, concluded that transmission of the novel coronavirus is likely to be seasonal in the post-pandemic period. Studies from University College London and Harvard University’s Royal School of Public Health have also found that the early implementation of strict social distancing measures is essential to controlling the spread of the virus, and that in the absence of new treatments or preventative measures, intermittent social distancing may be the only way to avoid overwhelming intensive care units while building herd immunity.
Insufficient data
The lack of data and information raises questions about the study’s findings, as the data used is limited to temperate subtropical regions, which represent only 60% of the world’s population. The study also assumed that a vaccine against the virus would not be discovered, whereas we expect a vaccine to be available within 12 to 14 months. Anan, who says the model assumed schools and universities would be closed for the duration of the study, explains that the available data on the virus’s seasonality is insufficient, as there is only five years’ worth of data available on infections with similar coronaviruses. Furthermore, there is a lack of data on herd immunity or acquired immunity.
He believes that developing a vaccine against the virus will change all the patterns mentioned in the study, “but the hope of producing a vaccine that can eliminate the virus 100% is not likely, and we can see that in the flu vaccine, which only reduces the likelihood of getting the flu, not eliminating it.”
The future and a spark of hope
At best, Kessler believes, we will be able to keep infections at a minimum until a vaccine becomes available, at which point the vaccine will provide the residual immunity needed to stop transmission. He explains, “Otherwise, we will have to gradually approach herd immunity and keep the number of cases low enough to avoid overwhelming healthcare systems.”
Kessler hopes a vaccine will be available in 18 months, saying: “If this happens, there will be no need for further modeling to predict the spread of the virus, and the epidemic should subside significantly once enough people have been vaccinated.”
Kessler explains the purpose of building this model: “We wanted to show what might happen if a vaccine isn’t available soon. There’s a lot of work to be done to prevent a surge in deaths and hospitals from being overwhelmed.” He adds, “We still have 18 months to go, which is a long time, and the virus could cause serious damage before it’s brought under control.”
With news emerging of a gradual return to normalcy in some countries, such as Germany, New Zealand, and Australia, people are clinging to the hope that life will soon return to normal. The study indicates that intermittent social distancing will vary in duration and frequency from place to place. Kessler explains, “These decisions must be made locally, taking into account the rate of transmission, the underlying risk factors within the population, such as the proportion of elderly people, rates of conditions like heart disease or diabetes, and hospital capacity.” Kessler believes the end of this pandemic will most likely be the achievement of herd immunity, when a sufficient proportion of the population becomes immune to the infection so that the disease no longer becomes an epidemic. Anan, however, believes the virus is likely to continue in waves, similar to H1N1 and other influenza viruses. He adds, “We have learned from history that humans adapt to the most virulent viruses, even in the absence of any treatment.”
0 Comments