Why Do We Need ‘Booster’ Shots of the COVID Vaccine?
When you take a ‘booster dose’, you’re building on immunity you already have from the first dose.
The COVID vaccine rollout is now underway in Australia and around the world. It’s incredible we’ve been able to develop and produce safe and effective vaccines so quickly — but the current crop of vaccines might not protect us forever.
Fortunately, researchers are already developing and testing booster shots. So what are booster shots, and when might we need them?
First a Prime, Then a Boost
The first time you give someone a dose of vaccine against a particular infection, it’s called a prime. You’re getting your immune response ready to roll.
Each time you give another dose against that same infection, it’s called a boost. You’re building on immunity you already have from the first dose.
Our immune cells essentially remember vaccines we’ve previously received, and respond much more quickly and vigorously to subsequent shots, building our immunity to levels at which we can be confident we’ll be protected.
When Might I Need a Boost?
There are three different situations in which you might need a boost.
First, several doses of a vaccine can be given relatively quickly, one after another, to rapidly build someone’s immunity against a given infection. A good example is the whooping cough vaccine.
It’s initially given at around two, four and six months of age to rapidly build immunity in infants, who are most at risk from whooping cough.
For example, we know immunity to tetanus can drop over time, so we recommend tetanus boosters every ten years.
Third, if the virus “mutates” or changes substantially over time, this can make it challenging for our immune cells to recognize the virus, effectively lowering our immunity again. A good example here is the influenza vaccine.
On the Front Foot With Viral Variants
SARS-CoV-2, the virus that causes COVID-19, has already undergone a number of changes. We’re still learning how this might affect the efficacy of different vaccines.
They’re intending to find out how well it works against B.1.351, the variant first identified in South Africa.
The updated vaccines tweak the “antigen” — the molecule used by our immune cells to target a specific virus. But they can use the same basic design and manufacturing processes.
More of the Same, or Something a Little Different?
With boosting, you can end up with a higher level of immunity if you wait longer between doses.
This is because our immune cells need a rest before they can respond to additional doses.
We’re not sure why a mix-and-match approach can be more potent. But it’s possible combining two different vaccines — which give the same antigen target but stimulate the immune system in different ways — could better focus our immune cells’ attention on the right target.
But that could change. While there are now multiple approved COVID vaccines, vaccine rollout has been challenging.
Australia will benefit from the knowledge these trials will bring, allowing us to fine-tune our boosting strategies, and maintain immunity in our population.
(This is an opinion piece and the views expressed above are the author’s own. The Quint neither endorses nor is responsible for them. This article was originally published on The Conversation. Read the original article here.)
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