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Breakthrough infections and vaccine efficacy: Why are vaccinated people still getting the virus?

Vaccines remain our best bet at protection, with breakthrough Covid cases forming a minority of the total volume of new cases.
Updated 22 Aug, 2021 11:15pm

Junaid Ahmed, 78, is currently in recovery from a breakthrough infection of Coronavirus. A resident of Karachi, Ahmed was vaccinated in April with the Sinopharm vaccine and remained in good health for several months before contracting the virus and experiencing debilitating symptoms, such as shortness of breath with a consistent drop in his Oxygen levels. It is pertinent to mention that this wasn’t Ahmed’s first brush with Sars-Cov-2 — he went through Covid-19 in August 2020 and was hospitalised for several weeks.

“This should not have happened to me…I was vaccinated. I did everything right,” Ahmed says over the telephone from his residence in Karachi’s Federal B Area neighbourhood.

However, the idea that one cannot get infected with the virus on account of vaccination is incorrect and shifts focus from the a critical function that the vaccine is meant to serve.

Vaccination still the best bet?

“Vaccination is more effective at preventing hospitalisation and death as compared to preventing infection, especially against the highly infectious Delta variant,” says Dr Abdul Bari Khan, CEO Indus Hospital Karachi.

He adds that “This is reflected in our observation, as many vaccinated healthcare workers still contracted Covid-19, though their symptoms remained mild. On the contrary 99% of our hospitalised patients are unvaccinated.”

Dr Faisal Mahmood, an infectious diseases expert from Aga Khan University Hospital in Karachi, says that while each variant is different in its ability to evade the immunity developed by vaccines and also that the immunity developed by each of the vaccines is different as well, one must not lose sight of the fact that “a lower immune response is not the same as no immune response”.

“In short, this is complicated and at this point we feel all vaccines are sufficiently good. As the data evolves we may have a clearer picture,” says Dr Mahmood.

Vaccination and what else?

Fatima Zehra, 45, a resident of Karachi’s Jamshed Town, recently recovered from a breakthrough infection, and wonders what she can do to protect herself and members of her family from getting sick with Covid-19.

“We are not one of those people who are anti-vaccines. All the adults in my household are vaccinated. But somehow, I still got sick and I had to be shifted to a hospital. Sure, I survived, but I’m already vaccinated and I don’t know what else I can do to protect myself and my family members,” Zehra says, anxious.

This is a question on many minds. Vaccinations are being done but cases haven’t gone down. And while a rise in case numbers also has to do with easing of restrictions, Dr Bari tells us that in the case of breakthrough infections, those may also be occurring due to “a false sense of security” among the vaccinated few.

He adds that vaccination is causing individuals to stop practicing essential SOPs e.g. wearing mask, physical distancing; people are back to working in ill-ventilated, crowded and small offices, are sharing food and drink with colleagues at work, and are using crowded public transportation.

This means that even though many of us may be vaccinated, we cannot abandon the SOP routine. And while vaccines offer us protection, if overall coverage is not sufficient, it makes it so much more difficult for us to resume the pre-Covid normal and drop some of the SOPs from our routines.

“Vaccines offer only modest protection against preventing infection. They prevent hospitalisations and complications better,” says Dr Bari.

He adds that if one looks at the published data on protection against most Covid variants, the mRNA vaccines — Pfizer and Moderna — demonstrate the most robust protection, followed by Astra Zeneca.

Dr Mahmood also shares the same sentiment on vaccine efficacy. He says: “Vaccines are good at preventing severe disease but may not be as good as preventing one from getting the infection to begin with.”

Booster shots to bolster protection

Ahmed and Zehra both wonder if they and their family members will be needing booster shots to bolster protection against the virus. And while booster shots are being administered in some parts of the world, they are currently limited to populations that are immunocompromised and with comorbidities. But will booster shots become a norm is a question many have been asking.

It is still too early to say anything definitively on this, says Dr Bari.

“Elderly and immunocompromised people may not be adequately protected. And some variants, like the Delta strain, may show immune escape and not be adequately covered by current vaccines. Having said that, from a public health stand point, it is very important to concentrate on strategies to maximise primary vaccination coverage and aim to vaccinate 60-70% of our population rapidly,” he adds.

Dr Mahmood says that if not now then eventually booster shots may become important.

An expected outcome

Vaccine sceptics and even some who have gone by the book here wonder if vaccines have failed at offering sufficient protection. However, both Dr Bari and Dr Mahmood disagree with the hypothesis.

“Breakthrough infections are an expected outcome post-vaccination and have been seen in many other infections as well e.g. measles, chicken pox. They do not denote a failure of vaccination as vaccine effectiveness is best seen with prevention of severe outcomes of Covid infection and in this respect the vaccine seems to be working,” says Dr Bari.

Dr Mahmood says in this situation expectations and reality need to be matched. “The expectation is that the vaccine will prevent infections. This is unlikely to ever be the case…For example, if theoretically we have 100% vaccination, then all cases coming to us will be breakthroughs. Also, even if a vaccine prevents 90% of severe illness, you may still see 10% who will get quite sick.”

In this situation and as data continues to evolve, it is safe to say that while breakthrough infections are occurring, vaccines remain our best bet at protection against Covid-19, with such cases forming a minority of the total volume of new cases.