Why countries abandoned ‘Zero Covid’ strategy

When SARS-CoV-2 virus began spreading globally early last year, Singapore, Vietnam, Taiwan, South Korea, Hong Kong, Australia and New Zealand, like mainland China, adopted a “Zero COVID” strategy. The goal was to aim for almost zero daily fresh cases through a mix of border closing, quarantining people coming into the country, extensive testing and strict implementation of COVID-appropriate behaviour. This not only greatly reduced daily fresh cases, it also led to fewer deaths and health-care facilities not being stretched. But even with a large percentage of the population vaccinated, most of these countries have begun reporting a large number of new cases due to the Delta variant. Some countries have now abandoned the strategy.

In an email to The Hindu, epidemiologist Dr. Giridhara Babu from Bengaluru’s Public Health Foundation of India explains why the Zero COVID strategy is impractical and difficult to sustain and what could be the best exit strategy to aim for.

Recently, despite over 83% of the population being fully vaccinated, Singapore made a dramatic switch from Zero COVID to COVID resilience strategy. Australia too has abandoned its Zero COVID approach. Even with over 61% fully vaccinated, Israel witnessed a surge in daily cases recently. Taiwan, Vietnam and Hong Kong, too, have reported large cases. So, can any country achieve Zero COVID and remain so for long with the Delta variant spreading wildly?

Zero COVID cases is a myth as an accomplishment for a longer time. Countries might be successful only for a transient period, but this will not be sustainable. Many countries which set the ambitious and unrealistic goal of achieving Zero COVID have abandoned it, as each of these countries is vulnerable to the ever-evolving virus.

Considering that fully vaccinated people, too, can get infected with the Delta variant and spread the infection, can any country remain without any fresh daily cases for a long period after fully opening its borders and resuming all economic activities?

No country can permanently shut its borders; with any mobility of people, the virus can only reach the susceptible nations. Countries cannot remain without fresh cases if the borders are opened, and when economic activities are resumed. Only countries with islands and relatively restricted travel could keep the virus in check, at least for a short period. Having no new daily cases is not practical due to its constant evolution.

Even as other countries are struggling, how is China able to effectively stamp out outbreaks within a very short time and almost achieve Zero COVID?

China has adopted a very hard on itself policy by repeated mass testing (to find out the missing cases), a complete cut-off of Beijing from the rest of the country, stringent curbs barring the inflow of people from high-risk to low-risk zones and very strict home isolation. These tough measures have helped China have a low number of COVID cases, but not sure if this can be replicated anywhere else or be sustained in China.

Israel’s coronavirus czar, Salman Zarka has already warned of another wave with new variants. He is talking of a fourth dose and has said that considering the waning of protection from vaccines, additional doses may be needed every few months. Does this reflect the hollowness of the Zero COVID strategy?

While the Zero COVID strategy is impractical, the idea of additional doses of vaccines is not completely backed by science. The countries advocating booster doses have done so mostly because of the country's failing strategy of COVID-19 control, type and dose of vaccine used and its coverage, and failure to prevent the susceptible population against the evolving virus. Isolated and individual country-specific responses against the virus are bound to fail. These countries can keep the infection at bay only for a short time, only to be infected later due to mobility. People in these countries are always at risk of getting infected with newer variants of the virus.

There are multiple challenges with the implementation of booster doses. If the initial doses of a vaccine have not prevented the spread of infection, additional doses also won’t be successful in this goal. For now, ensuring that every eligible person gets two doses in every part of the globe is more important. Even when implemented, acceptance of a greater number of vaccine doses by the public would be a very big challenge. The reactive response to breakthrough infections and mostly mild cases leads to unjustified demand for booster doses. This is derailing the global agenda from what actually needs to be done.

Though not eradicated like in the case of smallpox, many countries have eliminated (reduced case transmission to a predetermined very low level) malaria and measles. Is it possible for any country to work towards eliminating COVID-19?

A s long as the virus flourishes in any part of the world, no part of the world is safe. Isolated plans for COVID-19 elimination in a few countries through vaccination alone will not lead anywhere near elimination, even in those countries. We need a global control strategy and need vaccines available to scale to tackle the virus in every part of the world. Elimination of the virus in the short term is a difficult stand to take because even if a country manages to eliminate the virus, opening the borders will expose people to newer strains of the virus even if the country manages to strictly adhere to COVID-appropriate behaviour.

Since the SARS-CoV-2 virus has found new hosts in domestic and wild animals, can the virus be ever eliminated?

W hen elimination of this virus is infeasible, eradication is out of the question. Eradication of the virus means that it has to be completely exterminated; with the ever-evolving and virulent strains, we cannot rule out the virus finding new animal hosts. Adopting one health strategy to protect humanity against emerging zoonotic diseases should be an integral part of preparing for the future.

The virus is currently evolving to become increasingly more transmissible, lethal and reduce the protection conferred by vaccination or natural infection. So, under what conditions will we see the virus becoming endemic?

O nce the combination of acquired immunity and vaccination is achieved in every part of the world, it is expected that most regions may become endemic to SARS-CoV-2. Endemic means sustained transmission at an expected or basal level, although it’s not desirable. I do not see an alternative other than targeting endemicity as the exit strategy.

C onsidering that even fully vaccinated people can get infected but are very unlikely to progress to severe disease, should we stop fussing about daily fresh cases and instead look at the number of people hospitalised, number of severe cases, ICU bed occupancy and deaths? Should daily cases be categorised as reinfections, breakthrough infections and cases in unvaccinated people?

U ndoubtedly, WHO should begin with a newer case definition. The phobia surrounding the number of people who test positive should stop. It is time to revise the case definition to reflect those who need hospitalisation. Otherwise, the numbers will be inflated due to a combination of asymptomatic breakthroughs and false positives. Vaccination prevents hospitalisation and deaths. We need to continually monitor the breakthrough infections and hospitalisations among them in addition to recording reinfections. However, the goal of the newer case definition should be to prevent deaths and hospitalisation due to severe illness.