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When your child receives the Quadrivalent (DPT-IPV) vaccine, have you heard alarming stories from parents or grandparents about the old DPT (Triple) vaccine? Tales like "The side effects were terrible, I got a fever close to 40∘C," or "The injection site swelled hugely, and bathing was strictly forbidden."In fact, this perception is the true root of modern vaccination myths, such as "No bathing after the flu shot." The old DPT vaccine from the 1970s ∼ 80s was indeed a "vaccine of terror" with a high risk of severe reactions due to its manufacturing method.However, the current Quadrivalent (DPT-IPV) vaccine has evolved to a completely different level of safety. This article thoroughly explains the entire scope of this dramatic evolution—with the fever rate dropping from 50% to 1% and severe swelling becoming nearly zero—using a complete comparison chart with the old DPT.

Myths like "No bathing for 6 hours after the influenza vaccine" are deeply rooted for other vaccines as well. Many of these originated from "outdated manufacturing methods or fears of past infectious diseases" and have been successively withdrawn by the guidelines of the Ministry of Health, Labour and Welfare (MHLW), the Japan Pediatric Society, and the CDC. Below are the most common myths heard in Japan, explained with scientific evidence, detailing "why they were born" and "the truth."

After getting the influenza vaccine, have you ever been told by a nurse or doctor, "Please take only a shower today and wait 6 hours before taking a bath"? Although many hospitals now say, "You can go right away," this "6-hour post-vaccination waiting rule" stubbornly persisted as a long-standing custom in Japan.

After receiving the influenza vaccine, many people feel uncertain and have questions about daily life: "Should I avoid exercise today?" "Is it okay to take a bath?" "Can I drink alcohol?" In particular, the outdated information that "bathing is prohibited for 6 hours after vaccination" still persists, leading people to unnecessarily restrict their daily activities.However, based on the latest clinical knowledge in 2025, the conclusion is very simple: "If you adhere only to the 30-minute waiting rule, you can resume 100% of your normal life starting on the day of vaccination."

"My child developed a runny nose and a mild fever (37.2∘C) on the day of the appointment. Should I cancel?" — This is one of the most frequently asked questions every flu vaccination season. Many people hesitate, fearing that "side effects will be worse if vaccinated with cold symptoms" or "the vaccine will be ineffective because the immune system is weakened by illness."However, the latest scientific and clinical data in 2025 completely overturn this common concern.

When you or your child have symptoms like a runny nose, a light cough, or a slight fever—what we call "a slight cold"—on your appointment day, do you hesitate about whether to cancel the vaccination? Many people miss their chance due to anxiety like, "Will the side effects get worse?" or "What if the fever goes up?"This article puts an end to this long-standing question. It thoroughly explains the real criteria used in medical practice in 2025 to determine "Can be vaccinated / Postpone," based on symptoms and body temperature.

"I have an allergy, so I can't get it." "I get a fever every year, so I'm scared." — Many people who hesitate to get the influenza vaccine mistakenly believe they are "contraindicated" (people who cannot get the shot). However, this judgment of "cannot be vaccinated" is changing year by year due to medical advancements.

Don't give up on vaccination due to misunderstandings! An M.D. reveals the latest criteria for Egg Allergies, Pregnancy, and Ongoing Medical Treatment."Should I get vaccinated this year?" "Can I even get the shot?"—Every year, the influenza vaccine season brings questions and anxieties. Especially for those with egg allergies, those who are pregnant, or those undergoing treatment for chronic conditions like asthma, many instinctively hesitate, thinking, "Is it safer not to get it?"But is that judgment truly correct?As of 2025, due to medical advancements and the latest findings, the consensus is that 99.99% of Japanese people can receive the influenza vaccine, excluding only those who have had anaphylaxis to the vaccine in the past or those with a high fever on the day of vaccination. This article provides a definitive list based on the latest views from the Ministry of Health, Labour and Welfare and medical specialists, ending all your doubts by listing those who absolutely cannot be vaccinated, those who should be vaccinated, and the "common misconceptions."

For individuals with chronic illnesses (underlying conditions) such as diabetes, heart disease, or COPD (Chronic Obstructive Pulmonary Disease), influenza is not just a common cold; it is an extremely dangerous threat that increases the risk of severe illness, hospitalization, and death by 5 to 10 times or more. Especially since a highly virulent Type A virus is predicted to circulate in the 2025 season, vaccination is positioned as an "essential medical procedure to save lives."While the prevention of illness for people with underlying conditions may be a moderate 30% to 50%, the influenza vaccine demonstrates overwhelming figures for the prevention of severe illness (80% to 95%) and prevention of hospitalization (70% to 90%). Scientific evidence clearly shows that the mortality risk increases by 60% to 80% if the shot is not administered.

The side effects that occur after an influenza vaccination, such as "sore arm," "fever," and "malaise," are essentially "proof that your immune system has properly awakened" and is preparing to fight the virus.The true nature of the side effect is the release of inflammatory substances called "cytokines" by immune cells (macrophages) that recognize the foreign material (vaccine antigen) in the body. If these cytokines cause local blood vessels to dilate, it leads to arm swelling; if they stimulate the brain's thermoregulatory center, it leads to fever. Fever is an "immune strategy" designed to activate the immune system and is by no means a sign of a weak body.