Am I missing out on the new booster?

So everyone is able to get a fourth Covid-19 shot now….except if you’re in your twenties.

So everyone is able to get a fourth Covid-19 shot now….except if you’re in your twenties.

So everyone is able to get a fourth Covid-19 shot now, except if you’re in your twenties.

If you feel like you’re going to be way worse off than those who are about to line up for a fourth shot, you might be surprised to hear that there are parts of your immune system we never hear about that are still primed, on guard, and ready to fight coronavirus….even if it’s been many months since your third vaccination. 

First, this week’s news

The nation’s top vaccine experts, the Australian Technical Advisory Group on Vaccination, have just radically altered course on our booster program. They’re recommending that everyone over 50 now get a fourth shot, but they’ve also said that anyone over 30 is now free to get a second booster even though they’re not recommending it. It means Australians aged 30 to 50 are about to become the first healthy young people in the world to be able to get a fourth vaccination. 

ATAGI have been upfront about the fact that they don’t really know how much benefit a fourth shot is going to confer on younger people. If the effects in older people are replicated in the young, it’s likely to boost antibody levels back up to the level following a third dose, and reduce the chances of severe illness about four-fold. But the antibodies will decline rapidly, beginning after five weeks according to Israeli studies, and the protection from catching Covid-19 will only be transient.

It was partly this uncertainty about the net benefit to young people of a fourth shot that saw ATAGI draw the line at opening up a fourth shot to everyone. But there were two other big factors it took into account in deciding to exclude those in their twenties from a second booster.

Firstly, the chances of severe disease from Covid-19 in this age group is exceedingly low. Since the beginning of the pandemic in Australia, only 15 men and 13 women aged in their twenties have died from Covid-19 out of more than 10,000 fatalities. Of the 666 new admissions for Covid-19 to NSW hospitals in the past two weeks, 26 were aged in their twenties and none of those patients ended up in ICU.

There is also a very remote risk of a relatively serious side-effect of a Covid-19 vaccine that occurs more commonly in the young, especially men: inflammation of the heart. It usually resolves quickly, but the existence of such a risk and the uncertainty as to a fourth shot’s benefit meant that on balance ATAGI did not endorse allowing those in their twenties to get a fourth shot. 

Does this mean you’re left with no immunity if you’re in this age group?

If you haven’t had your third shot, the answer is yes because two shots won’t protect you against Omicron.

But if you have had your third shot, you’re actually still well protected against severe disease from Covid-19. Yes, if it’s been five or six months since your initial booster, your circulating antibodies against SARS-CoV-2 will have substantially dropped.

Antibodies are what we always hear about because that’s what pharmaceutical companies measure when they assess people’s immune response to a vaccine. But there are other parts of your immune system we never hear about which are primed by vaccination and will protect you from severe disease possibly for as long as a year after your third shot, as Garvan Institute immunologist Stuart Tangye explains. 

“I think the reason there's so much emphasis on antibodies is it's really easy to measure, you just do it from a blood test,” Professor Tangye says. “But that's just one part of your immune response.” 

Antibodies induced by a vaccine have a large role to play in protecting you from catching and fighting the virus. But the effects of the vaccine on B cells and T cells - the system known as cellular immunity - are also extremely important in protecting you from getting really sick. These cells variously produce antibodies, coordinate the immune response, and kill virally infected cells. And some of these cells are repositories of immune memory, making immune responses last longer.

Studies have not yet been done on how long the boosting of cellular immunity is sustained following three shots, but Professor Tangye is confident enough to say that those in their twenties should not panic about being barred from getting a fourth shot at this stage if they have had two initial shots and one booster. 

“I'd like to think protection lasts about 12 months,” he says.

“I don't think young people need to panic, they can be assured that they have a level of protection. It won't stop you getting sick, but it'll stop you getting really sick.” 

All of this is relevant of course to people in their thirties, too. Even the Royal Australian College of General Practitioners is not advising people in this age group to rush out to get a booster. If you want to, there’s absolutely no harm and it will confer an immune boost over the crucial winter weeks even if that wanes quickly. But this is unlikely to be the last vaccine available this year, with medical regulators currently preparing to approve variant-specific vaccines that have been developed by Pfizer and Moderna. 

“I think it is a reasonable assessment for people in their thirties and forties to make, to hold off for now,” says RACGP vice-president Bruce Willett. “But the people in that group who have other medical conditions and chronic diseases really should consider going ahead and getting it. And I would hope that they do.” 

ATAGI made a point this week of saying that public health measures like mask-wearing and social distancing are likely to be more effective than fourth doses in limiting the spread of Covid-19 in any event. 

That’s a point that Professor Tangye agrees with. “I think people still need to be conscious of all those other interventions - social distancing, mask-wearing, washing hands,” he says. “Not as not as intense as what we've lived through, but I still think people just need to practice those simple things.”