Do booster vaccinations prevent breakthrough infections? Who knows? But is that the right question. Are breakthrough infections important to prevent? Afterall we do know that most breakthrough infections are mild or asymptomatic.
When we look at deaths from COVID amongst breakthrough cases, they occur at a rate of one in 500,000 people vaccinated. The average age of those who died was 82 years. Compared with life general expectancy tables, an 82-year-old who is vaccinated and has a breakthrough COVID infection is more likely to live than the whole cohort of 82-year-olds.
Does this make sense?
So, what does the booster do? It decreases the amount of virus in an infected person’s body by a factor of 5.
That is important in trying to prevent spread as viral load is the go-to indicator of infectiousness. Unfortunately, positive PCR results, which measure viral load, cannot distinguish between viable and non-viable viruses. Studies of viral motion during infection have shown that there are no live viruses after day 9 of a COVID illness, despite persistently high viral loads. In addition, the rate of decline of viral load seems to be faster in vaccinated compared with unvaccinated people.
It also seems that viral loads appear to be similar between asymptomatic and symptomatic individuals.
Vaccine effectiveness is also measured by its ability to prevent severe infections and so far, booster vaccinations have resulted in only a slight decline in preventing severe disease.
So, reducing viral load by getting a booster shot will have very little impact on an individual’s relationship with COVID and there is some conjecture that further boosters may be offered or even required in some circumstances (to do what?). Breakthroughs, boosters and severe COVID – are they really related? More frequent vaccinations are certainly good news for the vaccine manufacturers, but we can only wonder why they aren’t making a vaccine to last as long as some of the other vaccines. The CDC is recommending booster shots six months after completing the initial course of COVID vaccination, while the influenza vaccine, for example, lasts a year.
Fortunately, we know what the risks for COVID are. The biggest one is age: increasing age adds between 10 and 30% risk for the five older age decades: 50-59, 60-69, 70-79, 80-89, 90+. Surprisingly, individual medical conditions, such as cancer, chronic lung disease, diabetes, heart disease, high blood pressure and kidney disease, add very little, that is less than 6% risk.
Assessing the cumulative effect of these risk factors has sent statisticians into a feeding frenzy. There is at least one new publication a day on the most recent algorithm to determine risk.
Then there are the risks we can minimize in our daily lives. Until the revaccination outcomes are clearer, we can use these algorithms together with assessing the risks in our daily lives. To create our own COVID algorithm to help us assess our own daily risk: consider vaccination, social distancing, minimizing close physical contact with too many people whose vaccination and booster status is unknown, and masking in confined spaces or locations with poor ventilation. Then we all must make our own choices based on the best available information, our individual appetites for risk, and our desire to protect ourselves and others. Now that the majority of us are fully vaccinated, it is time for governments to educate more and regulate less.