People around the world are eager to ditch COVID tests, social distancing and the fear of infection to return to life with concerts, cafes and hugs for family and friends. But how will we know when the pandemic is over?
A look to New Zealand and a small handful of other countries shows an example that billions of people would like to follow. Young people there show tens of thousands of people at a rock concert, packed together and bawling along to their favorite hits — without masks and without social distancing.
But a look to India shows the coronavirus still spreading with deadly and devastating effects. India's health system has collapsed beneath the strain of the country's second wave of COVID-19 infections. There isn't enough oxygen to treat people; corpses are left to float down the Ganges River. The death toll there from COVID-19 hit a new high on Wednesday when around 4,500 people died of the disease. Data from Johns Hopkins University shows no other country has reported so many deaths in a single day — and the true figure is assumed to be much higher.
The effect of vaccinations and variants
In between those coronavirus extremes, health officials and politicians debate what it will take to declare the end of the pandemic. So far, many of the answers were either vague or sobering and involved factors that can be difficult to influence.
Scientists initially said it would take around 60% to 70% of people being vaccinated to achieve herd immunity that will keep safe even those who have not been vaccinated. The assumption at the time was that if around 66% were immune because they had either recovered from the disease or had a vaccination, the reproduction number (R) would fall below 1. Statistically, one infected person would then infect less than one other, and the pandemic would peter out as a result.
Now, however, the assumption is that the novel coronavirus is more infectious than was initially thought, and scientists now believe that around 80% of people would have to be vaccinated for the pandemic to be brought to an end.
The variants are coming
The coronavirus variants first observed in the United Kingdom, South Africa, Brazil and India are also causing uncertainty because scientists estimate that these spread around 30% faster than the original virus. This means that almost 90% of people would need to be vaccinated before herd immunity could be achieved. The vaccines may also be less effective against the variants – the South African one in particular.
And it's not yet clear to what extent vaccination reduces transmissibility. So far, the manufacturers' findings suggest that vaccinated people are between 67% and 94% less likely to transmit the virus, depending on which vaccine they've been given.
When will we reach herd immunity?
Vaccination coverage is increasing
Even as the number of people vaccinated increases, it is questionable whether vaccination coverage of around 80% can actually be achieved in the coming months. The problem is that even if there is enough vaccine to go around, there will always be people who can't be the jab. These include, for example, people for whom the World Health Organization does not generally recommend vaccination at present, such as pregnant women and young children, or people who are allergic to any of the vaccine's components. Also, while the vaccines are believed to be between 67% and 95% effective in the majority of people, there is still the remaining percentage in whom they will not have the same effect. This includes immunosuppressed people, as their vaccine response is less robust.
Some don't want to be vaccinated
The United States is demonstrating how a vaccination campaign can falter. Since around mid-April, the number of vaccines being given each day has been dropping – and around 8% of people who have received the first dose don't then show up for their booster. In Europe, a recent study showed that over 20% of adults in the EU would likely turn down a vaccination if offered one.
The risks of vaccine scepticism
Post-pandemic is endemic
Even in countries with very high vaccination coverage, there is still a danger of catching COVID-19. Health officials warn that the virus is unlikely to be eradicated since it has spread worldwide; the most likely scenario is that it will keep coming back.
Nonetheless, on a slightly more hopeful note, they say they suspect that the virus will become endemic. This means that it will join the ranks of the seasonal cold viruses and may well end up becoming a childhood illness, insofar as children are not vaccinated against it. This is the situation Christian Drosten, director of the Institute of Virology at the Charite hospital in Berlin, envisages us being in in about 18 months' time.