Vaccine Victory Via Chickens

Dr Karl: G’day, Dr Karl here.

Very soon after the COVID-19 pandemic stormed around the world, people were asking if it were even possible to make a vaccine against this novel virus, SARS-CoV-2.

The veterinary pathologist, Dr Ian Tizard, from Texas A&M University, already knew the answer, and was yelling it at the TV. It turns out that veterinarians have been giving coronavirus vaccines for about half-a-century. Sure, they’ve been vaccinating chickens, but many millions of doses have been given with excellent outcomes. This suggests that we could also do the same for people.

To make any vaccine, you have to know what you’re up against. There are hundreds of coronaviruses, but let’s start simple. Coronaviruses are single-stranded RNA viruses. They’re spherical in shape, ranging from 60-220 nm in diameter. (A nanometre is a billionth of a metre. Compare that to the wavelength of blue light which is around 440 nm). Sticking out from their spherical body is a crown (or corona) of many spikes – hence the name “coronavirus”. The spikes are about 12-24 nm long.

These spikes are surprisingly large (for a virus). It’s an advantage, because it lets the spike adapt easily to new targets, and attack them.

But not only can coronaviruses easily mutate their spike protein, to better invade their target. They have another trick! When one coronavirus comes across a slightly different coronavirus, they can mix and match some of their genetic code and hey bingo! – there’s a new-kid-on-the-block.

In 2003, a coronavirus found in a dog, turned out to be almost identical to a cow coronavirus – which could also infect other animals such as horses, alpacas and pigs. And this specific cow coronavirus is now thought to be what set off the 1890 “Russian flu” pandemic, which killed over a million people.

Getting back to chickens, the very first coronavirus ever discovered was Infectious Bronchitis Virus, or IBV, back around 1937. This virus is the major pathogen that infects chickens worldwide. It attacks the lungs, causing pneumonia, and also targets their kidneys causing nephritis, which can stop the kidneys being able to function properly. It’s so contagious it can infect 100% of a flock of chickens within a single day.

Scientists developed the first commercial IBV vaccines about half-a-century ago.

So today, virtually every commercial chicken in the world is vaccinated against IBV. They usually get their first dose on the day they hatch, either being added to their drinking water, or sprayed into the air right around them. The longer they live, they more doses they get. And if there’s some new strains of IBV in the local area, they might get updated booster shots.

World-wide, this chicken coronavirus has over 50 different major types, and hundreds more minor variants. By mid-2020, in North America alone, there were about 57 different vaccines licensed for use in chickens by the United States Department of Agriculture. But of those, the vaccines most commonly used in the US differed slightly to what was used in China and Europe. That’s because different strains of the virus dominated in different parts of the world.

 So here’s the Big Picture.

In order to be able to continue commercial chicken production for the last half-century, veterinary immunologists have monitored the different strains of chicken coronavirus as they change, and matched them with regularly updated strains of chicken coronavirus vaccine.

Humans might have to head down a similar path.

Yes, it’s still early days for COVID-19 vaccines. But it might be that every year, we humans need to be vaccinated against whatever strains of SARS-CoV-2 happen to be in our local area. Which isn’t that different from getting your yearly flu shot.

If this stops us from getting sick, it’s an eggs-cellent!