![]() ![]() Unless a new generation of vaccines can provide much higher protection, regardless of emerging variants, the zero-COVID era will not return. But they need to move quickly to high vaccination coverage levels before these strategies start to crumble. And daily cases in Hong Kong have been in single figures since April. Taiwan successfully controlled its first big COVID wave between May and July 2021. And countries have started booster vaccine programmes to reinforce immunity in the elderly and vulnerable. But vaccine breakthrough – that is, fairly mild infections in those fully vaccinated – is now common. Therefore, the critical target for countries to reach is over 90% coverage in adults, which Denmark, Ireland and Portugal have reached. China has reached 75%, but Taiwan and Vietnam are lagging far behind.ĬOVID disease and transmission in children are uncommon. New Zealand and Australia, at 40%-50% coverage, are playing vaccine catchup and are at risk. The standout countries now are those, like Singapore, that kept case numbers and deaths low and moved quickly to reach high vaccine coverage levels. But the huge jump in virus transmissibility and the swift development of highly effective vaccines has forced changes in the response. No countries in Europe or the Americas attempted it. Zero-COVID has been effective at preventing deaths and allowing a certain level of normality within national borders in countries that moved rapidly to shut their borders, and where the geographical, political and economic factors were favourable. This is the difference between a possible 200 extra infections transmitted from a single case in three weeks, compared with 15 new infections with the original virus. The reproductive number, which is the average number of people that one infected person will pass on the virus to, averages 5.1 for delta, compared with 2.8 with the initial virus. The viral load, which is the concentration of the virus in the throat and nose, is 1,000 times higher with delta than with the original virus. Simple facts around the transmission power of the delta variant show how the ability of SARS-CoV-2 to mutate in conditions of rampant infection has been a gamechanger. Infectious diseases and our responses to them have both evolved. ![]() The most important lesson, however, is not to find and adhere to one strategy, but to steadily follow the science. ![]() There can be little doubt that countries that adopted a zero-COVID strategy saved thousands – if not hundreds of thousands – of lives. To a zero-COVID approach on the other end of the spectrum – as pursued by China. ![]() But countries with strong central political control, such as China, were also able to implement this strategy.Ĭontrol strategies lay on a spectrum, from a laissez-faire and chaotic approach characterised by denial, in the case of Brazil and a laissez-faire, civil libertarian approach of relying on disease-induced herd immunity, in the case of Sweden. Effective border quarantines were easiest for island nations. Different approachesĬountries that quickly closed their borders, once initial reports of a new epidemic emerged from China in January 2020, were able to put zero-COVID strategies in place and keep death rates low. How long they will continue with this strategy is anyone’s guess. China, Hong Kong and Taiwan are the remaining zero-COVID holdouts. ![]()
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