Last spring, when the inhabitants of half the world were shut inside their homes in an effort to stem the advance of the SARS-CoV-2 coronavirus that causes COVID-19, many people believed that the end of the pandemic was only a matter of weeks away, especially when some high-profile voices were propagating that message. During the summer, with the drop in the number of cases, the pandemic was already being discussed in the past tense and projections of economic recovery were being made, suggesting that the worst of the crisis was behind us. However, this was never the viewpoint of the expert scientists, who right from the start foresaw successive waves of infections and warned that the virus could be with us forever. At the end of this fateful 2020, vaccines are now a reality, and the start of immunisations in several countries gives us a glimpse of the ending of the pandemic. But is this really the case, or do we still have a long way to go to get back to normal?
One approach to predicting the future may be to look to the past. Humanity has suffered serious global epidemics throughout history, most notably the bubonic plague and the so-called Spanish flu of 1918. But if we can learn anything from historical pandemics, it’s that sooner or later they all end. However, they have not done so in the same way. The plague has resurfaced periodically, causing three major pandemics that only ended, it is assumed, when the surviving population acquired immunity. In the second of these, the Black Death of the 14th century, quarantine was introduced for the first time. More recently, smallpox was contained by vaccination and cholera outbreaks were brought under control by public health measures. But even in the 20th century, the 1918 flu caused between 40 and 100 million deaths.
A medical or social ending
Except for isolated examples such as smallpox and cholera, it is not really clear which key factors brought the past pandemics to an end, as various historians have told The New York Times. Did the climate play a role? Did the pathogens change or their hosts? Were the measures undertaken at the time effective? In the case of the 1918 flu, the virus evolved to become one of the seasonal flus that returns every year. However, experts distinguish between two types of endings to a pandemic: the medical ending, when the outbreak disappears, and the social ending, when fatigue leads people to lose their fear and try to get back to normal, even if the virus is still present.
The second is, of course, difficult to predict. But in terms of the medical ending of this pandemic, at least today we have a response that was unimaginable a few months ago: in a record time that is unparalleled in history, we already have safe and effective vaccines. Two of them, from Pfizer-BioNTech and Moderna-NIAID (US National Institute of Allergy and Infectious Diseases), both based on an RNA formulation, are now arriving in different countries, and others will follow. This suggests that vaccinations will mark the end of the pandemic, a forecast endorsed by various experts.
However, the Director General of the World Health Organisation, Tedros Adhanom Ghebreyesus, recently summed up the experts’ view by warning against the idea that the exit will be quick: “The pandemic still has a long way to run and decisions made by leaders and citizens in the coming days will determine both the course of the virus in the short term and when this pandemic will ultimately end.” NIAID Director Anthony Fauci, the main visible head of the fight against the pandemic in the US and head of the organisation that has collaborated in the creation of the Moderna vaccine, warned in October that masks and social distancing will have to continue, perhaps until 2022: “It’s not going to be the way it was with polio and measles, where you get a vaccine, case closed, it’s done. It’s going to be public health measures that linger for months and months.”
The acceptance of vaccines and herd immunity
One of the key questions that will influence the panorama of the pandemic over the coming year is the public acceptance of vaccines. Surveys in different countries reveal that a significant part of the population is suspicious of the safety of inoculations. Given that an estimated 70% of the population needs to be immunised to achieve herd immunity, either through vaccination or by virtue of having recovered from the illness, low vaccine penetration could delay the ending of the pandemic.
Another variable to be determined, and which will also be key when it comes to achieving herd immunity, is the effectiveness of the vaccines in the long term, especially in two aspects: the duration of the protection and the likelihood of vaccinated individuals contracting the virus and being able to transmit it. With regard to the former, differing studies on the duration of the presence of antibodies in the blood have appeared over the months, and there have been cases of people being reinfected, although these seem to be in the minority. However, it should not be forgotten that memory B and T lymphocytes, not detected in seropositivity studies, also play an essential role in immunological protection. In practice, the only way to know the duration of immunity in the long term will be to wait and see; there are no shortcuts to this.
As for the latter aspect, there is still no certainty. Clinical trials have assessed the efficacy of vaccines in preventing the disease, but this does not necessarily rule out the possibility that the virus may proliferate in the upper respiratory tract with the consequent risk that a vaccinated and infected person may in turn be a source of new infections. This does not invalidate the usefulness of vaccines, but could greatly affect the evolution of the pandemic, as well as warranting the extension of the social risk-prevention measures recommended by Fauci.
Even with these unanswered questions, “we can reasonably hope for an end to the pandemic in 2021,” concluded a recent data analysis from the McKinsey consultancy. But many experts are confident that the virus will remain among us even after the pandemic has subsided; only one human disease, smallpox, has ever been eradicated after a coordinated global effort that lasted for decades. Therefore, the experts also suggest that certain things may never be the same again. Historians say that past pandemics changed the world forever. Perhaps in the decades to come we will look back in wonderment at the days when we didn’t wear masks in health care facilities or on public transport, or when people actually shook hands to greet each other. And we may count ourselves lucky if that’s all we have to miss.