Vaccine stockpile could help in battling bird flu
H5N1 is potentially a far more serious threat than Covid-19. While it is too early to ring the alarm, it would be foolish to not be prepared
Bird flu is now rampant in mammals: Since 2021, 37 new mammal species worldwide have been affected including foxes, polar bears and cows. Entire colonies of sea lions and Antarctic seals have been decimated. One in five milk samples in the United States (US) is reported to carry the H5N1 virus although pasteurised milk is safe for consumption. Cows themselves are not at high risk and have only mild illness that resolves in about a week, but over half of the cats at the Texas dairy farm where cows tested positive for bird flu died after drinking raw milk.
Coming on the heels of the Covid-19 pandemic, which killed millions of people and caused significant economic damage, it is reasonable to ask whether and how long it will take for this virus to be a problem in India. How worried should we be and what should we be doing?
Let’s start with the areas of concern. First, H5N1 is highly pathogenic in birds and some mammals. In other words, it can cause severe disease or death. There have been 26 H5N1 cases reported in people in eight countries since 2022. Of these, 14 patients had severe disease, and there were seven deaths, which works out to a mortality rate of about 250 per thousand cases. In comparison, the mortality rate for Covid-19 is about two per thousand. An epidemic that is much smaller than Covid-19 in terms of the number of people infected could have the same kind of devastating consequences as the Covid pandemic if our experience with poultry transmitted-H5N1 is any guide.
Second, unlike with Covid-19 where the elderly were most at risk, with H5N1, it is possible that both the elderly and small children are at risk if the new strains behave the way that existing influenza viruses do.
Third, as with Covid-19, once H5N1 has adapted to humans, it is difficult to put the genie back in the bottle. In other words, we may be looking at annual vaccinations against H5N1 since the variant will change slightly every year and the consequences may be serious enough that we do want people to get vaccinated.
Fourth, there is evidence that the virus has been transmitted from cows to poultry, potentially via human carriers. If the virus is similarly transmitted to pigs, that would be of concern because pigs carry many respiratory viruses that also infect humans. Once the H5N1 virus is established in pigs, there is a greater likelihood that a strain that could efficiently transmit between humans will emerge. This could be a few months or many years away, but given the enormous risk it poses, this is not a risk one should take lightly.
But there are reasons for hope. First, there is no evidence yet of human-tohuman transmission, and as of now, people are not yet at risk. Any possible infections are only from close contact with infected animals and there has been no reported transmission of the virus from human to human. The one farmworker in Texas who contracted H5N1 only had a case of conjunctivitis. In fact, it is possible that the virus may never acquire that ability or that the strain that is able to transmit from human to human only causes mild disease. Second, the current strain of H5N1 appears to be treatable with a widely available generic drug oseltamivir. Third, unlike SARS-COV-2 which hit us without any warning, we have a lot of scientific evidence on the H5N1 virus. Unlike the coronavirus, the H5N1 virus has been studied for years, although it could yet mutate in ways that surprise us. And lastly, vaccines against influenza strains appear to be at least partially effective against H5N1 – a situation different from Covid-19, where we were starting from scratch to develop vaccines.
How can we be better prepared?
Our surveillance for new strains of influenza remains weak – to be fair, surveillance in animals even in high-income countries leaves much to be desired. Broader surveillance in wild animals in domesticated animals, as well as wastewater surveillance, are needed – without which we can only find the disease when it is reported in humans. That is simply too late.
Although H5N1 that is circulating appears to be treatable, that does not mean that everyone in the country has easy access to oseltamivir. A national stockpile of this drug, similar to that practised by the West, could be helpful in case there was a pandemic tomorrow. That does not guarantee easy distribution, but it could help avert the panic that results in patients trying to procure medications with questionable value at high cost.
Although India is a global hub for vaccine manufacturing, not all components of a vaccine are made in India. Importantly, the flu vaccines rely on a critical component called an adjuvant that makes the vaccine effective. It is not clear that there is enough supply of adjuvants to serve the world’s population in the case of an outbreak, and it may not be clear even what adjuvant we need until the first cases of human-to-human transmission occur and we can figure out the specific subtype of virus that is causing these infections. Other countries, including the US, have already been testing H5N1 vaccines including in children, who would be among the first to receive them.
Also, flu vaccines are still grown in eggs and scalability is an issue. Without a stockpile, which necessarily means that vaccines may go to waste if there is no epidemic, India will be late in catching up and the same situation where the vaccination came too late for millions of lives lost in the second wave of Covid-19 could occur. The Global South, including India, does not typically vaccinate against seasonal influenza and so our ability to scale up in the case of a pandemic flu virus is constrained. Last, but not least, as was the case with Covid-19 where humans had no previous experience with the virus, we are immunologically naïve concerning H5N1. Therefore, each person will likely need to receive two doses of vaccine to be protected.
While it is too early to ring the alarm, it would be foolish to not be prepared. There are many unknowns but one thing is certain. H5N1 is potentially a far more serious threat than Covid-19, and if we are counting on preparations after the first cases of humanto-human transmission, no amount of travel bans or airport closures (which are fairly ineffective incidentally) will be enough to save us.