Five major modelling studies reveal that suppression strategy might require multiple lockdowns until a vaccine is available. Governments must prepare themselves and society for such an eventuality.
- By Chandra Bhushan
As the number of Covid-19 cases nears half a million, governments worldwide seem to view lockdown as a way to control the epidemic. India too has decided to follow this approach and has just entered a three-week lockdown period. While there is widespread public support, questions arise about the approach, effectiveness and cost of strategy: Would one lockdown be sufficient to control COVID-19 epidemic, or would we require more? Should there be travel restrictions after the lockdown, especially international travel? Should the entire country be opened at once or should we open states on a case-by-case basis depending on the outbreak status? How do we sustain the economy, especially the livelihoods of poor and vulnerable, during multiple shutdowns?
Though definitive answers will be difficult, we now have several modelling studies on COVID-19 that can help us. To that end, I have considered the five most recent and recognised studies to probe the effectiveness of the lockdown strategy. These studies assess the efficacy of various Non-Pharmaceutical Interventions or NPIs (interventions without medicine or vaccine) in containing the outbreak. Two are specific to China, two to India and one study has modelled the effect of various interventions in the UK and the US.
Study 1: Impact of NPIs to reduce COVID-19 mortality and healthcare demand in the UK and the US
The study, led by Imperial College London, has reportedly influenced the strategy adopted by the UK and the US. The model tests two fundamental strategies: (a) Mitigation or herd immunity, which focuses on slowing, but not stopping, the spread. It relies on developing immunity in healthy population while protecting elderly who are most at risk, and, (b) Suppression, which aims to reduce case numbers to low levels and maintain it indefinitely through social distancing and lockdown.
The study finds that the mitigation strategy would result in hundreds of thousands of deaths and would overwhelm the healthcare systems in the US and the UK. It, therefore, finds the suppression strategy to be the most viable option. But, the major challenge of suppression is that lockdown needs to be implemented intermittently until a vaccine becomes available, as the transmission is likely to rebound once interventions are relaxed.
Study 2: Effect of NPIs for containing the COVID-19 outbreak in China
This study, done by an international team of researchers, models the effectiveness of various containment strategies used in China and validates the findings with actual case numbers. The study finds that without NPIs, there would have likely been 5 million Covid 19 cases in China, instead of 80,000. It also finds that China could have reduced the number of cases dramatically had it acted early. For instance, if Wuhan had been locked down and testing and isolation of confirmed & suspected cases begun in late December 2019 instead of late January 2020, China would have seen less than 5,000 cases-and the chances of the pandemic would have reduced significantly.
The study found a considerable difference in the efficacy of different NPIs. Early detection and isolation of cases followed by contact reduction and social distancing were found to be most effective; travel restrictions had a relatively lower impact. However, a combination of all NPIs achieved the most robust and rapid result. It concludes that if population contact resumes to normal levels, the epidemic could rise again. Therefore, social distancing and enhanced testing and isolation should be continued for several months, once lockdown and travel restrictions are lifted.
Study 3: The effect of human mobility and control measures on the COVID-19 epidemic in China.
This study uses real-time mobility data from Wuhan and detailed patient data from different parts of China to understand the role of travel restrictions. The study finds that travel restrictions from the epicentre of the epidemic (Wuhan) were particularly useful in the early stage of the epidemic. But once the outbreak was more widespread, travel restrictions were less effective. The study also found a good correlation between improved testing and slowing down of the epidemic.
Study 4: COVID 19 in India: Guidance from the IndiaSIM Model
The research done by the US-based Center for Disease Dynamics, Economics & Policy (CDDEP), uses an India-specific model-IndiaSIM-and data from China and Italy to simulate the outbreak in India. It has simulated three scenarios-from least optimistic to most optimistic -and has estimated country as well as state-level total cases and hospitalisation cases.
As per this model, without interventions, 300-400 million Indians can get infected by July. At the peak (between April and May 2020) 100 million individuals can be affected, of which about 10 million will be severe, and about 2-4 million will require hospitalisation. Social distancing, however, can reduce this peak by as much as 75%. In all scenario examined by the model, the case number is likely to peak after April-end, and a recurrence of the epidemic can be expected in November/December.
The study doesn’t recommend an international travel ban or a national lockdown. It recommends lockdown of highly-affected states/areas, social distancing, large-scale testing, separation of COVID 19 patients from other patients in hospital (because of high chances of hospital outbreaks in India), temporary hospital facilities for severe cases and upgradation of hospital infrastructure including personal protective equipment and ventilators.
Study 5: Prudent public health intervention strategies to control the coronavirus disease 2019 transmission in India: A mathematical model-based approach
The study was recently released by the Indian Council of Medical Research (ICMR). It aims to answer two questions: (a) Is it possible to prevent, or delay, the local outbreaks of COVID-19 through restrictions on travel from abroad, and, (b) If the community transmission has started, then to what extent can it be controlled through quarantine of symptomatic patients? The study has simulated various scenario of the outbreak in the four most populated metropolitan areas (Delhi, Mumbai, Kolkata and Bengaluru).
The study finds that travel restrictions have little impact on the outbreak as most asymptomatic patients would escape detection and cause onward transmission in the community. It, however, finds that it may be possible to interrupt the transmission of COVID-19 in India by aggressive quarantine of symptomatic cases (optimistic scenario). However, even in the pessimistic scenario of suboptimal quarantine, the peak cases can be reduced, resulting in the ‘flattening of the curve’. This would reduce the peak demand on health services, but would have minimal effect on the overall number of cases.
The study recommends enhanced surveillance of symptomatic patients followed by testing and quarantine to interrupt the transmission of COVID-19 in India. It is remarkable how closely all five studies agree with each other. It is, therefore, easy to summarise their findings and recommendations. From the above studies, the following can be concluded: Early intervention is the right approach: The Centre’s lockdown decision at a low number of detected cases seems to be supported by the models.
Be prepared for a long haul: Suppression strategy requires multiple lockdowns because the epidemic would likely return once the restrictions are lifted. So, governments and businesses should prepare an action plan for at least 12 months, until we have a viable vaccine to build immunity in everyone.
To avoid lockdown, mass testing and social distancing is the only answer: Mass screening and social distancing have been identified as the most effective tool. China-specific studies show that decline in case numbers started with mass-testing. As China was able to detect and isolate the infected persons and their contacts quickly, it did not require a nationwide lockdown. Similarly, mass testing and social distancing have significantly controlled the outbreak in South Korea. South Korea has developed rapid diagnostic tests (RDTs) that can give result in 10 minutes. It has set-up drive-through testing centres, testing tents, and is distributing at-home testing kits. Such RDTs are urgently required.
Travel restrictions without mass testing are ineffective: In all modelling studies, travel restrictions were found to be highly ineffective because most asymptomatic persons couldn’t be identified at the port of entry. Without an effective method to detect all infected persons, travel restrictions have very little value. So, once travel restrictions are removed, mass screening with RTDs should be instituted at all airports and entry points.
State/hotspot lockdown more effective than national lockdown: A state/hotspot lockdown seems to provide a better trade-off between health and economy than a lockdown. So, it would be better to implement targeted lockdown in the next phase of the epidemic. Similarly, instead of opening the entire country at once, the status of the outbreak in states should prompt case-by-case decisions.
Social support programme is essential: The experience of the last four days clearly shows that the informal sector, migrant workers, landless workers, poor women and children are the worst-hit in the lockdown. Governments must put in place a social support programme to provide them with essentials, including food and hygiene products.
Health infrastructure: Last, we must invest in healthcare infrastructure quickly before the cases overwhelm us. Temporary hospitals, personal protective equipment, ventilators and mass production of test kits is urgently required. Similarly, regulators should quickly clear all possible drugs that are useful in the prevention and treatment of COVID-19.
It is essential to understand that governments across the world are enforcing lockdown with a hope to conquer the disease quickly, even if there is a short-term economic shock. But, what happens if the COVID-19 is not suppressed quickly? Are governments ready for multiple lockdowns and the resulting financial setbacks? I guess that no government is even contemplating these scenarios. But as the above modelling studies show, these are real possibilities, and we must plan for these eventualities. The experience of the past pandemics is that it is better to be overprepared than underprepared. The cost of not planning ahead is just too high.
(The author is CEO, iFOREST. Twitter: @Bh_Chandra. Views are personal.)