Seasonal influenza programs can be cornerstones to pandemic preparedness and response. Using the 2009 WHO Vaccine Deployment Initiative as a case study, eligible countries with a seasonal influenza vaccine program were more ready to receive and use donated vaccines than those without a program. These findings suggest that robust seasonal influenza vaccine programs allow countries to test crucial regulatory and delivery systems that enhance pandemic preparedness while also reducing the substantial burden of seasonal influenza.
Influenza
Immunization can prevent severe respiratory infections in children, reducing hospital admissions and deaths worldwide
A systematic review of the global burden of acute lower respiratory infections associated with seasonal influenza in children under 5 years found that just in 2018 these infections led to an estimated 870,000 hospital admissions and 15,300 in-hospital deaths. About 23% of these hospital admissions and 36% of the in-hospital deaths were in infants under 6 months and about 82% of the in-hospital deaths occurred in low-income and lower-middle-income countries.
Influenza vaccine for pregnant women in Bangladesh led to fewer respiratory illnesses in their infants
Pregnant women in Bangladesh who received the influenza vaccine had elevated levels of anti-influenza antibody in their breast milk. The infants of mothers who received the vaccine during pregnancy had fewer episodes of respiratory illness with fever than the infants of mothers who did not receive the influenza vaccine during pregnancy. Further, exclusive breastfeeding was found to have a protective effect against respiratory illness with fever in infants.
Immunization during pregnancy reduces the risk of stillbirths and preterm delivery caused by influenza
During the 2009 UK influenza A H1N1 pandemic, pregnant women who contracted influenza were five times more likely to have perinatal mortality (stillbirths) and three times more likely to have a preterm delivery, than were pregnant women who did not contract the virus.
Immunization during pregnancy reduces the risk of miscarriages, stillbirths, low birthweight, and premature deliveries
Studies from multiple Western countries have found that pregnant women infected with influenza during the 2009 A/H1N1 pandemic were at higher risk of miscarriages, stillbirths, low birthweight and premature deliveries. The risk of fetal death was between 2 and 5.5 times higher in pregnant women with influenza than in pregnant women without influenza. In the UK, the rate of stillbirths was 4.5 times higher and the likelihood of preterm delivery was 4 times greater in influenza-infected pregnant women than non-infected women.
Although this article indicated that influenza vaccination is safely used for the mother and the fetus, conflicting data exists on the effect of vaccination in improving preterm birth rates.
Vaccinated children missed fewer school days compared to unvaccinated children
In a study of school-based influenza vaccination in Los Angeles County, California, children who were vaccinated missed significantly fewer days of school than children who were not (2.8 vs. 4.3 per 100 school days).
Immunizing school-aged children against the flu reduces the risk of infection for everyone in the community
School-aged children (5-18 years old) experience the highest attack rates of influenza of any age group and are thus the most important means of spread of infection in the community, making them crucial targets for influenza vaccination. In a study of school-based influenza vaccination in Los Angeles County, California, schools that offered flu vaccine to their students reduced the risk of any child getting the flu by 30% (regardless of vaccination status) compared to schools that did not offer flu vaccine to students.
Influenza vaccination during pregnancy reduces severe pneumonia rates in infants, especially during peak influenza circulation
An analysis of data from three studies showed that the rates of severe pneumonia in infants in their first six months of life was 20% lower overall in infants whose mothers received the influenza vaccination during pregnancy than in infants whose mothers had not, and the rates of severe pneumonia was 56% lower during periods when influenza circulation was highest. These findings correspond with evidence that influenza infection predisposes individuals to pneumococcal infection.
The incidence rate of severe pneumonia in the vaccine group compared to the control group was 43% lower in South Africa, 31% lower in Nepal, but not significantly different in Mali.
Influenza vaccines reduce antibiotic use by preventing secondary infections and unnecessary prescriptions for respiratory illnesses
Vaccines against influenza reduce the use of antibiotics that drive drug resistance in bacteria in two ways. First, they prevent secondary bacterial infections caused by influenza, such as pneumonia and otitis media; in Ontario, Canada, the rate of prescribing for influenza-associated antibiotics declined around 64% after universal introduction of influenza vaccination compared to other Canadian provinces with more limited use of the vaccine. Second, they help prevent inappropriate antibiotic prescriptions for respiratory tract infections caused by influenza and other viruses, which account for half of all respiratory illnesses for which antibiotics are prescribed in the U.S.
Immunization during pregnancy protects against serious illnesses and improves pregnancy outcomes
Pregnant women are at particularly high risk of serious illness and death from a variety of bacterial and viral diseases, such as influenza, pneumococcal pneumonia, and Group B strep, for which vaccines exist or are in development. Vaccine-preventable diseases in pregnancy are associated with adverse pregnancy outcomes such as spontaneous abortion, congenital anomalies, preterm birth, and low birth weight.