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.
Complete Guide to Influenza Vaccination “For People with Underlying Conditions”
Individuals with underlying conditions have a 5 to 10 times higher risk of severe illness, hospitalization, and death from influenza infection, making vaccination strongly recommended. As of 2025, guidelines from the Ministry of Health, Labour and Welfare and the Japanese Association for Infectious Diseases prioritize vaccination for people with diabetes, heart disease, respiratory illness, kidney disease, and immunodeficiency, making early vaccination key to saving lives.
| Type of Underlying Condition | Risk of Severe Illness | Recommended Shot | Notes (2025 Latest) |
| Diabetes | 5–8x | ◎ Absolute Must-Get | Poor control (HbA1c≥7.0) causes immune suppression (20–40% reduced efficacy). Consider 2 doses. |
| Heart Disease (Heart failure, angina) | 6–10x | ◎ Absolute Must-Get | High risk of myocarditis. Fluad recommended for ≥70% hospitalization prevention. |
| Respiratory Illness (COPD, asthma) | 7–12x | ◎ Absolute Must-Get | High rate of pneumonia complications. Early October vaccination protects the respiratory system. |
| Kidney Disease (Chronic renal failure) | 4–7x | ◎ Absolute Must-Get | Immunity is weak during dialysis. Recombinant vaccine is available for egg allergies. |
| Immunodeficiency (High-dose steroids, chemotherapy) | 10x or more | ◎ Get the shot if possible (Must consult doctor) | Antibody levels may be low. Family vaccination provides indirect protection. |
| Cerebrovascular Disease(Post-stroke) | 5–9x | ◎ Absolute Must-Get | High risk of encephalopathy. High-dose vaccine reduces mortality by ≥50%. |
| Cancer / HIV | 8–15x | ○ Get shot upon doctor’s judgment | Live vaccines are prohibited during treatment; only inactivated vaccines are used. |
2025 “Best Vaccination Strategy for Those with Underlying Conditions”
| Item | Details (For those with Underlying Conditions) |
| Priority Vaccination Period | October 1st – October 25th (Priority window for high-risk individuals). General public starts Oct 26th, but chronic patients should book early. |
| Number of Doses | Generally 1 dose, but individuals with weak immunity may consider 2 doses (2–4 weeks apart). 2 doses are mandatory for those under 13. |
| Recommended Vaccine | Fluad (High-Dose): 4x antigen for 1.5–2x antibody increase (≥65 and high-risk patients’ strongest option) / Recombinant Vaccine: OK for egg allergies, highest class of efficacy. |
| Effectiveness (Actual Data) | Illness prevention 30–50%, Severe illness prevention 80–95%, Hospitalization prevention 70–90%(Nearly twice the rate of illness prevention). |
| Side Effect Caution | Side effects may be milder if immunity is suppressed by illness, but heart/kidney patients must manage hydration strictly during fever. Anaphylaxis risk is standard. |
| Cost / Subsidy | Chronic patients are often eligible for medical expense subsidies (Self-pay 1,000–2,000 with 30%copay). ≥65 is nearly free. Local subsidies reduce cost further. |
| COVID-19 Co-vaccination | OK (Can be given on the same day). Recommended due to the high risk of severe illness if both epidemics strike. |
Scientific Evidence Why Those with Chronic Illnesses “Must Get the Shot” (2025 Data)
- Mechanism of Severe Illness: Underlying conditions weaken immune and organ function, making Type A influenza (H1N1), which is predicted to circulate in 2025, more likely to cause pneumonia and myocarditis.
- Evidence: Meta-analysis shows that vaccination reduces the hospitalization rate in chronic patients by 70%. Not getting the shot increases the mortality risk by 60%–80%.
- Doctor’s Honest Opinion: “If you have a chronic illness, there is no option not to get the shot. Too many cases result in hospitalization due to pneumonia when the illness would have been just a mild cold with the vaccine.”
At-Home Testing Kit Ranking (Combined COVID-19 and Influenza)
Here is the English translation of the ranking table for at-home diagnostic kits that test for both COVID-19 and Influenza A/B:
| Rank | Product Name (Manufacturer) | Targets Detected | Sensitivity (Detection Rate) (Estimate: 12-48h Post-Onset) | Result Time | Approximate Price (Per Test) | Suitability for Pregnant Women / Children | Key Features & Availability |
| 1 | Panbio COVID-19/Flu A&B | COVID + Flu A/B | COVID: Approx. 90% | Flu: Approx. 85% | 15 mins | ¥1,980 – ¥2,480 | ◎ (Shallow Nasal Swab) |
| 2 | クイックナビ-Flu+COVID | Same (COVID + Flu A/B) | COVID: 88% | Flu: 80–85% | 15–20 mins | ¥1,780 – ¥2,200 | ◎ (Designed for children’s use) |
| 3 | KBMラインチェック nCoV/Flu | Same (COVID + Flu A/B) | COVID: 85% | Flu: Approx. 80% | 15 mins | ¥1,480 – ¥1,980 | ◎ |
| 4 | イージードック Flu＆COVID-19 | Same (COVID + Flu A/B) | COVID: 87% | Flu: 82% | 15 mins | ¥2,200 – ¥2,600 | ◎ (Many cases of use by pregnant women) |
