Coronavirus breakthrough infections: Factors which make it easier for someone to get COVID-19 after vaccination

So far, there have been umpteen reports of a number of people having contracted COVID-19 after being vaccinated. While we now have credible proof of immunity peaking weeks following getting the jab, there's also some evidence to suggest that the immunity we gain in the first place can wane over time and make us susceptible to some risks again.

However, that's not the only possible reason for one to get a breakthrough case.

As per recent statistics, a mere 0.2%, or 1 out of 500 people tend to get a breakthrough case post-vaccination.

While breakthrough COVID infections are relatively milder, and cause fewer symptoms than an unvaccinated case, the alarming presence of newer variants, and, a few differential factors as with the vaccines themselves could determine the odds of catching COVID-19 weeks, or perhaps months after vaccination.

Just like the disease itself, some people are at a higher COVID-19 risk after being fully vaccinated, than others. Apart from the waning immunity and variants of concerns, there could be some other risk factors which could raise one's risk of getting a breakthrough infection. As we speculate the arrival of a possible third COVID wave, here are some of the reasons and factors to take into consideration:

Vaccination drives have been in place for a little over 8 months now, with several at-risk groups given prioritization. While early vaccination granted these groups some benefits and prevention, it could also mean that the ones who have been previously fully vaccinated could now face a greater risk of infection, if more virulent strains come up and immunity continues to destabilize. The length of time passed since vaccination is also an important factor to be considered, since we now have greater proof that vaccines do not tend to grant long-term immunity, and 6-8 months would be the average length of vaccine-generated antibodies to protect us. Of course, there can also be cases wherein a past infection + vaccination could lead to hybrid immunity, and protect them for longer.

Particularly, people with early vaccination, and those who face a higher risk threshold, such as healthcare workers could be more at risk in the current scenario.

All the coronavirus vaccines we have are said to surpass WHO safety standards, and have proven to be well-efficacious. But that doesn't mean that all vaccines are equal, and provide the same level of protection. The benefits and immune protection profiles are similar, but not standard. This means that certain vaccines could be much more suited for someone, or some vaccines could potentially flag off higher risks of breakthroughs. Hence, while it's important to get jabbed with any vaccine available to you, weighing relative risk reduction, i.e. how much an individual COVID-19 vaccine lessens risk of infection compared to unvaccinated population, is necessary. Also comparable are odds of symptomatic illness, severity, transmission, and other safety profiles.

While there's ongoing clinical study on the matter, comparative evaluations and real-world data have pointed out that the Modera and Pfizer mRNA vaccines offer a 95% reduction in symptomatic illness, while Jannsen vaccine offered a 60% reduced risk. With the Astrazeneca (Covishield) shot, there is a 70% reduction, which could be scaled up to over 80% if the gap between doses is lengthened.

While we talk of a possible third wave or the chances of more breakthroughs emerging, it's also important to ascertain the type and severity of risks we are facing, with the variants which may be present. A prior immunity gained against Delta variant may prove beneficial, but as we know, most vaccines tend to lower down protections with such variants. If more virulent strains, which cause more severity are to be seen, vaccines could further prove less effective.

Of course, while vaccine developers are working on upgraded versions , with more time, we could possibly evade this problem. But there's a long time for that to happen.

When we talk of contracting COVID-19 after vaccination, what's also important to compare is the individual risk factors and how well-equipped, or robust our immune response is. While it is important to keep following COVID appropriate behaviour, vaccine efficiency and protection also depend on individual risk factors- including preconditions, age, illness history and genetic makeup. Not only does immune response tend to decline with age, comorbidities and chronic immunosuppressive conditions can reduce the vaccine efficiency, and raise risks.