"COVID-19 Vaccine Reduces Aftereffects? ... Generally True" [Reading Science]

NYT "Majority of Studies Confirm... Some Papers Say No Relation"

[Asia Economy Reporter Kim Bong-su] The COVID-19 pandemic is now in its third year. Especially after the spread of the Omicron variant in December last year, cases of infection among those who received the third dose increased explosively, but recently the number of cases has clearly started to decline. South Korea's health authorities have begun to ease social distancing measures, considering the transition to an endemic phase manageable through the routine healthcare system. Meanwhile, a significant number of people suffer from long Covid, experiencing long-term aftereffects even after recovering from COVID-19. These aftereffects, which manifest as headaches, muscle pain, joint pain, loss of smell and taste, allergies, fatigue, and vision loss, are known to trouble recovered patients for over a year. Interestingly, many studies have shown that receiving the COVID-19 vaccine reduces the likelihood of these aftereffects compared to those unvaccinated, drawing considerable attention.

According to the New York Times (NYT) on the 26th (local time), numerous studies emphasizing the effect of COVID-19 vaccines in reducing aftereffects have been published. The UK Health Security Agency analyzed eight research papers released before mid-January and found that six of them reported fewer aftereffects in vaccinated individuals compared to unvaccinated ones. However, the remaining two papers suggested that vaccines do not decisively reduce aftereffects.

Notably, two relatively large-scale studies found preventive effects of vaccines against aftereffects. Among the papers analyzed by the UK Health Security Agency, one surveyed about 1.2 million patients using a mobile app and found that vaccinated individuals had approximately a 50% lower probability of developing aftereffects. Another study involving around 6,000 infected individuals reported that vaccinated people had a 41% lower risk of aftereffects.

On the 25th, when the 4th COVID-19 booster vaccination for those aged 60 and over who made advance reservations began, a citizen is receiving the vaccine at Bumin Hospital in Gangseo-gu, Seoul. April 25, 2022 Photo by Joint Press Corps (Portrait rights consent obtained)

Large-scale studies conducted in the United States showed similar results. 'Arcadia,' a US healthcare data company, examined health records of approximately 240,000 patients infected with COVID-19 until the end of 2021. They found that those who received one vaccine dose had a 1 in 7 to 1 in 10 chance of experiencing two or more aftereffects between 12 and 20 weeks post-recovery. Particularly, individuals vaccinated once after infection had a lower probability of aftereffects than unvaccinated patients, and the earlier the vaccination after infection, the lower the likelihood of aftereffects. In Israel, people who completed two vaccine doses had a 54% to 82% lower chance of experiencing headaches, muscle pain, and various other aftereffects compared to unvaccinated patients. Conversely, about 70% of unvaccinated individuals suffered from long Covid for an extended period.

A study conducted through the St. Louis Veterans Health Care System in the US also found preventive effects of vaccination against aftereffects. The research team compared about 42,000 unvaccinated infected patients with 16,000 vaccinated infected patients and found that vaccinated individuals generally had a lower probability of experiencing aftereffects such as lung disease and blood clotting. For other aftereffects, the reduction was only slight.

However, some studies report no preventive effect of vaccination on aftereffects. A UK research team analyzed health records of about 10,000 vaccinated patients and a similar number of unvaccinated patients through the US electronic medical record system and found that vaccination before infection did not reduce the risk of most aftereffect symptoms. The researchers noted, however, that vaccination lowered the risk of some symptoms such as abnormal breathing and cognitive impairment. This study was limited as it focused only on patients with severe aftereffects and did not include those with mild, everyday symptoms.

Scientists have yet to precisely analyze the reasons why vaccines reduce COVID-19 aftereffects. The causes of long Covid remain unclear. Various symptoms latent in different patients are emerging. Some suggest that remnants of the virus or genetic material persisting after recovery may be responsible. Another theory attributes aftereffects to blood circulation disorders or inflammation caused by an excessive immune response. Akiko Iwasaki, a professor of immunology at Yale University, stated, "Antibodies generated by the vaccine may remove viral remnants, providing vaccinated individuals with ongoing protection against aftereffects. However, for those experiencing symptoms caused by post-viral responses similar to autoimmune diseases, the vaccine may only offer temporary relief, and symptoms like fatigue may recur."

So, is vaccination effective for those already suffering from aftereffects? The NYT reported, "Earlier this year, some patients with aftereffects experienced improvements in brain fog, joint pain, shortness of breath, and fatigue after vaccination. However, since then, few aftereffect patients have reported symptom improvement post-vaccination, and some have even experienced worsening symptoms."