Vaccines, one of the healthcare sector’s greatest tool, essentially works by administering a weakened version of an infective pathogen and allowing the body to build up a natural immunity against such disease. While all vaccines confer a high degree of immunity, the duration of this immunity varies between short-term to long-term effects. For example, Hepatitis B vaccination confers long term immunity only requiring periodic booster shots. Meanwhile, influenza vaccination – or more commonly known as the flu shot – confers only a short-term vaccination requiring annual booster shots. But matters most is the safety profile of vaccines which often go through stringent tests before being passed by the public health sector. Now, the influenza vaccine is garnering much debate as new studies suggests that the shot may be linked to a higher risk of miscarriage in pregnant women.

Surprise findings into influenza vaccination

The result of a population study, published in the journal Vaccine, found that pregnant women who received influenza vaccination may be at a higher risk of suffering a miscarriage. Nonetheless, this is only if they had received the same vaccination the year before. These oddly specific set of results was captured from a study on the 2010 – 2011 and 2011 – 2012 influenza seasons and have left researchers and the scientific community puzzled. So much so, that even the authors of the paper have been cautious in jumping to conclusions based on the findings of their own report.

“I understand it’s disconcerting. It’s not a message that we welcome or want. But it is what we found, and we have an obligation to let people know about that,” said senior author of the report Dr Edward Belongia, a long-time vaccine researcher who heads the Centre for Clinical Epidemiology and Population Health at Wisconsin’s Marshfield Clinic. Dr Belongia also sits on the expert panel that helps makes vaccine policy recommendations to the Centres for Disease Control and Prevention (CDC).

Following the release of these results, the same group of researchers are hard at work analysing similar data from the yester-years to confirm the reliability of their data and ensuring that it was not just an unobserved statistical fluke. Nevertheless, the preliminary data has left many healthcare experts including the CDC with many questions. Especially since the CDC recommend that pregnant women in their second or third trimester to receive influenza vaccination and have continued to do so since the late 1990s.

Of the data studied between the year 2010 to 2012, the study focused on 485 women had miscarriages linked to influenza vaccination.
Of the data studied between the year 2010 to 2012, the study focused on 485 women had miscarriages linked to influenza vaccination.

Vaccine’s commitment to public health

Despite all the confusion humming around the situation, experts have advised the public and healthcare sector to proceed with vaccinations. This is in large part to the nature of the study which is both observational in nature and lacking a sizable group of women. For starters, observational studies lack the ability to make strong causative links due to their lack of placebo-control as a group of comparison. Moreover, the report only takes a small horizontal slice of a much larger vertical timeline that is the progress of influenza vaccines. By only looking at 485 women, during the study period, who miscarried, the numbers are much too small to form any reliable, conclusive data.

“We’re really sort of at the beginning of this process with this study. I have no doubt that we will eventually sort this out,” said Belongia. In the meantime, Belongia recommends pregnant women to continue with influenza vaccination.

“There’s a large amount of data and studies confirming the safety of flu vaccine in the second and third trimester. And the benefit is proven, and the safety is rock solid,” he elaborated. “And we want to be really sure that people don’t get the mistaken message that this study is suggesting that getting a flu vaccine at any time in pregnancy might be risky.”

Understanding the caveats in their data, the research team is now hard at work to repeat the same study while expanding their result over three years starting in 2012 – 2013. Due to the massive amount of data and the implications of the study, the team have also decided to be more meticulous in their approach and are not expecting results until 2018 or early 2019. Such moves are necessary in reiterating vaccine’s commitment to improving public health where constant and persistent research are carried out in ensuring the safety profile of vaccines.

The Malaysian landscape of influenza vaccination

Over in Malaysia, top healthcare professionals have been advocating for influenza vaccination; especially those in high-risk groups. Dr Christopher Lee, Sungai Buloh Hospital’s Head of General Medicine, has recommended for annual influenza vaccination as protection against severe influenza infections as well as death. Those who were particularly vulnerable included children, the elderly, pregnant women, healthcare works as well as those with chronic immune deficiencies. “If people in these categories get vaccinated, there is a 50% – 70% chance of risk reduction. Therefore, for those people in the risk categories, we would advise them to get vaccinated every year because it does protect them,” Dr Lee said.

This comes of the back of several influenza A related death which occurred in Terengganu earlier this year. Now equipped with the proper infrastructure, Dr Lee has urged the general public to receive their annual flu vaccination be it from government institutions of private healthcare clinics and hospitals.

Dr Lee went on to add the importance of education and awareness in the general public regarding influenza. The Malaysian public often confuses influenza with the common cold under the umbrella term of “flu”. This mistake could prove to be fatal especially in pregnant women who fail to receive their influenza vaccination. By adopting the CDC’s vaccination recommendation in pregnant women, Dr Lee hopes that the number of influenza cases and subsequently deaths in pregnant women can be drastically reduced.

The bottom line

Despite the recent study which indicated a possible link between influenza vaccination in pregnant women and an increased risk of miscarriage – due to the lack of causative links and reliable data from the initial investigation – current CDC recommendations to vaccinate pregnant women against influenza in their second and third trimester still stands. Depending on the results of the follow up studies, the stance of countries advocating for influenza vaccination in pregnant women, such as Malaysia, may shift drastically. At least for now, vaccines still possess a significantly greater advantage over its perceived harm. MIMS

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