The scale and speed of the global vaccination effort has been a triumph for humanity but it’s also important to manage expectations. The delta variant’s transmissibility and ability to evade some of the protection conferred from the vaccines means a certain number of people will catch COVID-19 post-vaccination, although its harshest effects should be blunted in most people. A new study analysed this specific cohort to understand more about the effectiveness of the vaccines and the symptoms of breakthrough infections to spot.
At the largest medical centre in Israel, researchers identified breakthrough infections by performing extensive evaluations of health care workers who were symptomatic (including mild symptoms) or had known infection exposure.
From December 19, 2020, to April 28, 2021, a total of 91 percent of the centre personnel received two doses of the Pfizer vaccine.
According to the researchers, this period was followed by a rapid decrease in newly detected cases.
“Simultaneously, efforts were extended to identify new cases with the use of daily health questionnaires, a telephone hotline, extensive epidemiologic investigations of exposure events, and contact tracing of infected patients and personnel,” they wrote.
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On January 20, 2021, the researchers initiated the study among health care workers at Sheba Medical Center, 11 days after the first staff members had received a second dose of the Pfizer vaccine.
Data were collected for 14 weeks, until April 28. Concurrently, the third and largest COVID-19 pandemic surge emerged in Israel and reached its peak on January 14, 2021, with reports of an average of 8424 daily cases.
The study goal was to identify every breakthrough infection, including asymptomatic infections, that occurred during the study period among the health care workers at the centre.
Among 1497 fully vaccinated health care workers, 39 breakthrough cases were detected.
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The most common symptom that was reported was upper respiratory congestion (36 percent of all cases), followed by myalgia (28 percent) and loss of smell or taste (28 percent) and fever reported in 21 percent.
On follow-up questioning, 31 percent of all infected workers reported having “residual” symptoms 14 days after their diagnosis.
At six weeks after their diagnosis, 19 percent reported having “long COVID-19” symptoms, which included a prolonged loss of smell, persistent cough, fatigue, weakness, dyspnea (shortness of breath), or myalgia (muscle aches and pain).
“In this study, we found that although the BNT162b2 [Pfizer] vaccine is extremely effective, rare breakthrough infections carry an infectious potential and create a special challenge, since such infections are often asymptomatic and may pose a risk to vulnerable populations,” the researchers concluded.
There is a chance you might still get or spread COVID-19 even if you have a vaccine, so it’s important to follow advice about how to avoid catching and spreading COVID-19.
What’s more, the COVID-19 vaccines approved for use in the UK have met strict standards of safety, quality and effectiveness.
They can cause some side effects, but not everyone gets them.
“Any side effects are usually mild and should not last longer than a week,” notes the NHS.