Could the COVID-19 vaccine end up becoming something like the seasonal flu vaccine, requiring people to be vaccinated every year? Scientists don’t rule that out.
The number of COVID-19 cases in cases in India will soon cross the 8-lakh mark, with 26,506 new cases being reported in a single 24-hour period. India’s active cases now stand at 2.76 lakh while 4.95 lakh people have recovered from the disease. Meanwhile, the death toll has risen to 21,604, with 475 new deaths recorded in a day.
India continues to be the third-worst affected country in the world after the United States and Brazil.
However, India’s numbers hide as much as they reveal. This is because the outbreak is following very different trajectories in different states.
For example, Maharashtra, the country’s worst-hit state, has recorded 2.3 lakh cases and 9,667 deaths so far.
Meanwhile, Uttar Pradesh, India’s most populous state, has reported a total of 32,362 cases and 862 deaths – which has to be seen in relation to the fact that UP is home to an estimated 23 crore people.
So how the pandemic progresses will depend a lot on how individual states are able to contain it.
The good news is that elimination can occur. New Zealand appears to have achieved elimination and other countries, such as Vietnam, South Korea and Australia may soon follow suit. But in many countries, including India, Covid-19 seems to be the unwanted guest who just will not leave.
Whether countries have been fairly successful in controlling their outbreaks (for example Germany and Denmark), or less so (for example the UK and the US), we generally see a rapid rise and relatively slow and uncertain decline in the daily case numbers.
In fact, it is often unclear whether the numbers will tail off towards zero (as in New Zealand), will surge back up (as in Iran), or will simply hover around some baseline level.
Simple scenario 1. An outbreak can end because herd immunity develops.
In this scenario, disease sweeps through the population, slowing as more and more infected people recover and acquire immunity. The duration of the outbreak depends on the size of the population, and daily new cases eventually tail off to zero. We see the symmetric rise and fall reminiscent of Farr’s law and can surmise that some process like this was behind the data which led Farr to his law. At the end of the outbreak, the proportion who have been infected depends on the basic reproduction number – the so-called “R0 value” – of the epidemic. Simulations suggest it would not be much below 80% for Covid-19, a devastatingly high figure.
Simple scenario 2. An outbreak can end via the introduction of strong “physical distancing”. This should be read to include increased hygiene, mask wearing, avoidance of gatherings, and all behaviours that reduce infection spreading.
In this simulation, physical distancing begins suddenly, and is strong enough to reduce R below 1. Daily new infections drop immediately and eventually tail off. In real data, we should, within a couple of weeks, see a clear drop in daily cases. With plausible levels of physical distancing, infections tail off more slowly than they rise, and Farr’s law is violated. A noteworthy feature of this scenario is that if mitigation occurs early enough in an outbreak, then only a small proportion of the total population will end up being infected.
More realistic scenarios
Neither simple scenario is able to explain the evolution of Covid-19 outbreaks in general. Firstly, seroprevalence studies have shown that Covid-19 outbreaks – even bad ones as in New York City and London – have not resulted in sufficient immunity to explain the drop-off in infections. Secondly, the data tells us that physical distancing after mitigation is, in general, insufficient to bring R immediately below 1.
Nevertheless, both physical distancing and herd immunity are key to controlling Covid-19. Following lockdown, physical distancing slows transmission; but most importantly lockdown localises disease. To put the latter effect in a simple-minded, but conceptually useful, way: lockdown divides people into those who belong to a community – a household, a close social network, a care home – where there is infection, and those who do not.
A long, hard slog
So, Covid-19 outbreaks do not just end. Stringent and effective measures can reduce transmission and localise disease to the extent that – in the best-case – transmission can then be brought effectively to zero through rigorous testing, tracing and isolation.
While this might be the gold standard, the more common reality will likely be that infection is beaten back to relatively low levels, but persists there for months, with occasional new surges until, hopefully, a vaccine is found. The “relatively low levels” will vary widely between different countries/states/cities. Caution and some level of acquired immunity will slow new outbreaks, giving testing, tracing and isolation a better chance of working.
Perhaps most important of all will be surveillance to identify developing hotspots, followed by well-rehearsed containment measures to stop the export of disease to new areas. In a large country like India, elimination may be achieved locally; but in every area one should always expect some spread under the radar and new introductions.
Basically, dealing with Covid-19 is going to be a long, hard, slog. But badly hit countries like the UK, the USA, and Brazil, provide a warning that, despite the difficulties, bringing infection to low levels and maintaining it there must be a priority. The toll from high levels of infection should not be measured only in Covid-19 fatalities, but also in the widespread loss of access to healthcare, the long-term health complications that can follow Covid-19 infection, the disruption to economic and social activity, and the diminishing of life that accompanies widespread fear and uncertainty.
- One of the most effective vaccines out there is the measles vaccine, which is known to be 97 per cent effective
- If a similar vaccine for COVID-19 is developed by, say, the spring of 2021, the world would have hit a jackpot
- But more realistically speaking, we might be looking at a vaccine which is 75 per cent effective
It’s a question the world is asking: When – and how — will this pandemic end? The answer is not simple, and it depends on which expert you speak to. But the overall medical consensus appears to be that a real end to the COVID-19 outbreak will have to wait till a vaccine is developed.
But that immediately raises a host of questions. First, what if we don’t get a vaccine or if we don’t get one in the next few years? That is not such a remote possibility. Remember HIV-AIDS still does not have a vaccine though the disease has been around for 40 years.
Secondly, what if the vaccine is not very effective? Again, this is very much in the realm of possibility. In fact, no vaccine is 100 per cent effective. One of the most effective vaccines out there is the measles vaccine, which is known to be 97 per cent effective. People who get two doses of the vaccine are protected from measles for life.
If a similar vaccine for COVID-19 is developed by, say, the spring of 2021, the world would have hit a jackpot – and it would signal the end of the pandemic, once the logistics of vaccinating the world’s 8 billion people are tackled.
But more realistically speaking, we might be looking at a vaccine which is 75 per cent effective. Dr. Anthony Fauci, the US’s top infectious disease expert, said last week that he would “settle” for a Covid-19 vaccine that is 70 to 75 per cent effective.
The thing is the coronavirus could be mutating in ways that would make any new vaccine possibly ineffective after a six-month period. We know that the influenza flu shot that millions of Americans take every year lasts only for that season, and people are encouraged to take it every year. In fact, it is even called the ‘seasonal’ flu vaccine.
Could the COVID-19 vaccine then end up being something like the seasonal flu vaccine, requiring people to be vaccinated every year? Researchers don’t rule that out.
From the point of view of the virus, ‘success’ would mean becoming as common as the common flu, so that it can pass on from host to host every year, year after year. For the more immediate future – the rest of 2020 – we can only hope that the combination of social distancing (which will keep the most vulnerable among us safe) and partial herd immunity will cause the virus to circulate less and less on its own. But the dangers of sudden outbreaks in pockets will continue.
The second type of ending
All of the possibilities mentioned above are to do with the physical or medical endgame of the pandemic. But medical historians and experts who have studied past pandemics tell us that there is also another type of ending – the “social” ending.
This is a fascinating concept and essentially implies that the population (or a large section of it) are no longer afraid of the virus, or tired of the disruption to their lives, and get back to business as usual. Such a phenomenon was seen in the 1918 Spanish Flu pandemic, with people desperate to get back to normalcy after the combined trauma of World War 1 and the outbreak (the latter killed an estimated 50 million people worldwide). But it appears that the Spanish Flu ended socially and medically at around the same time, allowing people — at least those not under colonial rule — to quickly return to a productive economic and social life.
With the coronavirus, it’s possible that it will end socially before it ends medically – we are already seeing signs of that in the US in states like Arizona, Texas, Florida and California where many young people are starting to socialise like before even though the virus is circulating in the community and infections continue to rise.
There is a hint of this happening elsewhere too – people are simply fed up of the coronavirus and the sacrifices involved in combating it. The price that we might have to pay for this lag between the social and medical end of the pandemic remains to be seen.