No, estos estudios no demuestran que la vacuna contra la gripe en niños pequeños sea "totalmente ineficaz"

A German blog has claimed that influenza vaccines for young children are “completely ineffective,” citing several studies. However, this assertion is misleading and lacks solid evidence. The claims were made by the Austrian blog TKP in late May, which suggests that the flu vaccine might cause more harm than benefit. These statements have been widely circulated online, with some users repeating the claim without verifying its accuracy. The blog references a study conducted in Spain, which reportedly found no measurable effect of vaccination on illness rates among children aged zero to two and two to four years, nor a decline in hospitalizations or protective effects for other age groups. The study was carried out by researchers in Catalonia, northeastern Spain, and published in April 2026. It examined the relationship between the 2023/24 nationwide influenza vaccination program for children aged six months to five years and the number of influenza cases and hospitalizations across all age groups. Approximately 10,000 patients who tested positive for influenza or received a diagnosis in the hospital were included in the study. According to the authors of the study, the introduction of the flu vaccination program for young children did not result in a decrease in flu cases or hospitalizations related to the flu. However, this does not prove that the vaccine is “completely ineffective.” The researchers themselves point out that several factors could explain the lack of observed population-level protection. One key factor is the low vaccination rate. In the 2023/24 and 2024/25 seasons, vaccination rates were estimated at around 19% and 27%, respectively, well below the levels needed to achieve herd immunity, according to other studies suggesting that rates of 50–60% would be necessary. Another contributing factor is the introduction of rapid tests for influenza in December 2020. This change may have led to overreporting or misclassification of cases, as prior years likely saw underreporting due to limited testing availability. Additionally, the effectiveness of the influenza vaccine can vary from year to year, depending on how well the strains included in the vaccine match the circulating viruses. The Robert-Koch Institute explains that influenza viruses constantly mutate, so vaccine manufacturers must update the composition of the vaccine annually to keep up with these changes. The blog’s argument is further supported by content from Nicolas Hulscher, a self-proclaimed epidemiologist associated with the McCullough Foundation, a U.S.-based private foundation known for spreading misinformation about vaccines. Hulscher’s blog has previously disseminated false information during the COVID-19 pandemic, which has since spread through social media platforms. The blog TKP has also been criticized for publishing inaccurate or misleading information in the past. While the blog presents selective findings from studies, it omits crucial context and draws conclusions that go beyond the data. For example, the Spanish study focused on population-level outcomes rather than individual protection, meaning that even if the vaccine had little impact on reducing overall infections, it could still offer benefits to vaccinated individuals. Furthermore, the study acknowledges that lower vaccination rates may have contributed to the lack of observable public health benefits. The implications of such misinformation extend beyond academic debate. Public trust in vaccines can be undermined by repeated exposure to unverified claims, potentially leading to decreased immunization rates and increased risk of disease outbreaks. Health authorities emphasize the importance of relying on peer-reviewed research and official guidelines when evaluating vaccine safety and efficacy. As the situation continues to evolve, experts urge continued monitoring of vaccine performance and public education efforts to counteract misinformation. The scientific community remains committed to transparency and rigorous evaluation of vaccine effectiveness, ensuring that public health decisions are based on accurate, comprehensive data.