A 2011 study found that seasonal flu shots increase the risk of flu by 73% and doubled the risk of non-flu respiratory infections.
https://doi.org/10.1097/inf.0b013e318201811c
A 2011 study confirmed that annual influenza vaccination indeed hampers the development of a robust cell-mediated immunity. Annual vaccination for influenza, “may render young children who have not previously been infected with an influenza virus more susceptible to infection with a pandemic influenza virus of a novel subtype.”
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3209321/
A 2018 study found there was an increase of acute respiratory infections caused by non-influenza respiratory pathogens following influenza vaccination compared to unvaccinated children.
https://www.sciencedirect.com/science/article/pii/S0264410X18303153?via%3Dihub
Children who get the flu vaccine have 3x the risk of being hospitalized for flu.
https://www.sciencedaily.com/releases/2009/05/090519172045.htm
A 2014 study found that the more the people had been vaccinated in prior years, the less effective the vaccine is at preventing the most recent season’s dominant H3N2 virus.
As they put it, “vaccine-induced protection was greatest for individuals not vaccinated during the prior 5 years.”
https://www.ncbi.nlm.nih.gov/pubmed/25270645
Not only are there serious questions about the efficacy of the flu vaccine, there is evidence to suggest that getting the vaccine every year may cause damage to the immune system.
In a 2016 study, researchers found that people who were vaccinated against the flu three years in a row were actually at higher risk of being infected with the flu.
https://academic.oup.com/cid/article/63/1/21/1745238
Increased Risk of Noninfluenza Respiratory Virus Infections Associated With Receipt of Inactivated Influenza Vaccine
https://academic.oup.com/cid/article/54/12/1778/455098?searchresult=1
A randomized controlled trial in 2012 found that influenza-vaccinated children had no significantly lessened risk from influenza and also a higher risk of infection from non-influenza viruses.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3404712/
Influenza virus made stronger by vaccines:
Flu vaccine increases risk of upper respiratory infection:
https://www.ncbi.nlm.nih.gov/m/pubmed/22423139/
Flu vaccine makes people >6x more infectious than non-vaccinated when they contract influenza A:
http://www.pnas.org/content/early/2018/01/17/1716561115
2014 study - Influenza-like illness was more common in children vaccinated against influenza
https://www.ncbi.nlm.nih.gov/pubmed/?term=24483149
https://www.ncbi.nlm.nih.gov/pubmed/?term=29348203
A study that compared children who received the flu vaccine to those who did not found the same rate of influenza in both groups following vaccination. It also found that the group of children who received the flu vaccine had a 4.4 times higher rate of non-influenza respiratory tract infections.
https://academic.oup.com/cid/article/54/12/1778/455098
Annual influenza vaccination hampers the development of virus-specific CD8(+) T cell responses
https://pubmed.ncbi.nlm.nih.gov/21880755/
Vaccination may make flu worse if exposed to a second strain
https://m.medicalxpress.com/news/2013-08-vaccination-flu-worse-exposed-strain.html
A review in the medical journal The Lancet found a lack of health benefits from influenza vaccine in children under two along with significantly increased rates of vaccine-related adverse events.
https://www.sciencedirect.com/science/article/abs/pii/S0140673605179847
A study published in Pediatrics International of Japanese children ages 6 months to 2 years who were vaccinated against the flu found that the influenza vaccine did not reduce the rate of influenza A infections in children under two.