Frequently Asked Questions
What is seasonal influenza (flu)?Seasonal influenza, commonly called “the flu,” is caused by influenza viruses, which infect the respiratory tract (i.e., the nose, throat, lungs). Unlike many other viral respiratory infections, such as the common cold, the flu can cause severe illness and life-threatening complications in many people. It is estimated that in the United States, each year on average 5% to 20% of the population gets the flu and more than 200,000 people are hospitalized from seasonal flu-related complications. Flu seasons are unpredictable and can be severe. Over a period of 30 years, between 1976 and 2006, estimates of flu-associated deaths in the United States range from a low of about 3,000 to a high of about 49,000 people. Some people, such as older people, young children, pregnant women, and people with certain health conditions, are at high risk for serious flu complications. The best way to prevent seasonal flu is by getting a flu vaccination each year. Flu vaccines protect against the influenza viruses that research indicates will be most common during the upcoming season. Everyone 6 months and older should get vaccinated against the flu every year. Get vaccinated soon after vaccine becomes available in your community, ideally by October. Immunity sets in about two weeks after vaccination. Flu Symptoms & Severity. peak of flu season has occurred anywhere from late November through March. The overall health impact (e.g., infections, hospitalizations, and deaths) of a flu season varies from year to year. CDC monitors circulating flu viruses and their related disease activity and provides influenza reports (called “FluView”) each week from October through May. See Weekly U.S. Influenza Summary Update. reports on influenza (flu) activity in the United States each week from October through May. The U.S. influenza surveillance system consists of five separate categories.
- Laboratory-based viral surveillance, which tracks the number and percentage of influenza-positive tests from laboratories across the country, and monitors for human infections with influenza A viruses that are different from currently circulating human influenza H1 and H3 viruses;
- Outpatient physician surveillance for influenza-like illness (ILI), which tracks the percentage of doctor visits for flu-like symptoms;
- Mortality surveillance as reported through the 122 Cities Mortality Reporting System, which tracks the percentage of deaths reported to be caused by pneumonia and influenza in 122 cities in the United States; and influenza-associated pediatric mortality as reported through the Nationally Notifiable Disease Surveillance System, which tracks the number of deaths in children with laboratory confirmed influenza infection;
- Hospitalization surveillance, which tracks laboratory confirmed influenza-associated hospitalizations in children and adults through the Influenza Hospitalization Network (FluSurv-NET) and Aggregate Hospitalization and Death Reporting Activity (AHDRA); and
- State and territorial epidemiologist reports of influenza activity, which indicates the number of states affected by flu and the degree to which they are affected.
Infant Immunizations FAQs
Q: Are vaccines safe?
A: Yes. Vaccines are very safe. The United States’ long-standing vaccine safety system ensures that vaccines are as safe as possible. Currently, the United States has the safest, most effective vaccine supply in its history. Millions of children are safely vaccinated each year. The most common side effects are typically very mild, such as pain or swelling at the injection site.
Q: What are the side effects of the vaccines? How do I treat them?
Q: What are the risks and benefits of vaccines?
A: Vaccines can prevent infectious diseases that once killed or harmed many infants, children, and adults. Without vaccines, your child is at risk for getting seriously ill and suffering pain, disability, and even death from diseases like measles and whooping cough. The main risks associated with getting vaccines are side effects, which are almost always mild (redness and swelling at the injection site) and go away within a few days. Serious side effects following vaccination, such as severe allergic reaction, are very rare and doctors and clinic staff are trained to deal with them. The disease-prevention benefits of getting vaccines are much greater than the possible side effects for almost all children.
Q: Is there a link between vaccines and autism?
Q: Can vaccines overload my baby’s immune system?
Q: Why are so many doses needed for each vaccine?
A: Getting every recommended dose of each vaccine provides your child with the best protection possible.Depending on the vaccine, more than one dose is needed to build high enough immunity to prevent disease, boost immunity that fades over time, make sure people who did not get immunity from a first dose are protected, or protect against germs that change over time, like flu. Every dose of a vaccine is important because they all protect against infectious diseases that are threats today and can be especially serious for infants and very young children.
Q: Why do vaccines start so early?
A: The recommended schedule is designed to protect infants and children by providing immunity early in life, before they are exposed to life-threatening diseases. Children are immunized early because they are susceptible to diseases at a young age, and the consequences of these diseases can be very serious, and even life-threatening, for infants and young children.
Q: What do you think of delaying some vaccines or following an alternative schedule?
A: Children do not receive any known benefits from following schedules that delay vaccines. Infants and young children who follow immunization schedules that spread out shots–or leave out shots–are at risk of developing diseases during the time that shots are delayed. Some vaccine-preventable diseases remain common in the United States, and children may be exposed to these diseases during the time they are not protected by vaccines, placing them at risk for a serious case of the disease that might cause hospitalization or death.
Q: Haven't we gotten rid of most of these diseases in this country?
A: Some vaccine-preventable diseases, like pertussis (whooping cough) and chickenpox, remain common in the United States. On the other hand, other diseases prevented by vaccines are no longer common in this country because of vaccines. However, if we stopped vaccinating, even the few cases we have in the United States could very quickly become tens or hundreds of thousands of cases. Even though many serious vaccine-preventable diseases are uncommon in the United States, some are common in other parts of the world. Even if your family does not travel internationally, you could come into contact with international travelers anywhere in your community. Kids that are not fully vaccinated and are exposed to a disease can become seriously sick and spread it through a community.
Q: What are combination vaccines? Why are they used?
Q: Can't I just wait until my child goes to school to catch up on immunizations?
A: Before entering school, young children can be exposed to vaccine-preventable diseases from parents and other adults, brothers and sisters, on a plane, at child care, or even at the grocery store. Children under age 5 are especially susceptible to diseases because their immune systems have not built up the necessary defenses to fight infection. Don’t wait to protect your baby and risk getting these diseases when he or she needs protection now.
Q: Why does my child need a chickenpox shot? Isn’t it a mild disease?
Q: My child is sick right now. Is it okay for her to still get shots?
A: Talk with the doctor, but children can usually get vaccinated even if they have a mild illness like a cold, earache, mild fever, or diarrhea. If the doctor says it is okay, your child can still get vaccinated.
Q: What are the ingredients in vaccines and what do they do?
A: Vaccines contain ingredients that cause the body to develop immunity. Vaccines also contain very small amounts of other ingredients—all of which play necessary roles either in making the vaccine, or in ensuring that the final product is safe and effective.
Q: Don't infants have natural immunity? Isn't natural immunity better than the kind from vaccines?
What are vaccines? "Vaccines help our bodies make protection against life-threatening infectious diseases," says Anne Schuchat, MD, director of the CDC's National Center for Immunization and Respiratory Diseases.When a germ invades the body, the immune system recognizes it as a foreign invader. This sets off a cascade of events. The immune system makes antibodies, which are specialized molecules that stick to the invader and either inactivate it or mark it for destruction. Specialized immune cells also seek out and destroy germs and cells in which germs are multiplying. Other immune cells remember the germ so the next time a germ of the same kind tries to invade the body, the immune system will be able to mount an immediate response. Vaccines offer a shortcut to immunity by raising protective immune responses before a germ invades. This gives the body a crucial head start that lets it prevent dangerous infections or make them less severe.
What is the flu shot?The flu shot is a vaccine given with a needle, usually in the arm. The seasonal flu shot protects against the three or four influenza viruses that research indicates will be most common during the upcoming season.
- Standard-dose trivalent shots (IIV3) that are manufactured using virus grown in eggs. Different flu shots are approved for people of different ages, but there are flu shots that are approved for use in people as young as 6 months of age and up. (Most flu shots are given with a needle. One flu vaccine also can be given with a jet injector, for persons aged 18 through 64 years.)
- An intradermal trivalent shot, which is injected into the skin instead of the muscle and uses a much smaller needle than the regular flu shot. It is approved for people 18 through 64 years of age.
- A high-dose trivalent shot, approved for people 65 and older.
- A trivalent shot containing virus grown in cell culture, which is approved for people 18 and older.
- A recombinant trivalent shot that is egg-free, approved for people 18 years and older.
What Would Happen If We Stopped Vaccinations?Before the middle of the last century, diseases like whooping cough, polio, measles, Haemophilus influenzae, and rubella struck hundreds of thousands of infants, children and adults in the U.S.. Thousands died every year from them. As vaccines were developed and became widely used, rates of these diseases declined until today most of them are nearly gone from our country.
- Nearly everyone in the U.S. got measles before there was a vaccine, and hundreds died from it each year. Today, most doctors have never seen a case of measles.
- More than 15,000 Americans died from diphtheria in 1921, before there was a vaccine. Only one case of diphtheria has been reported to CDC since 2004.
- An epidemic of rubella (German measles) in 1964-65 infected 12½ million Americans, killed 2,000 babies, and caused 11,000 miscarriages. In 2012, 9 cases of rubella were reported to CDC.
If one or two cases of disease are introduced into a community where most people are not vaccinated, outbreaks will occur. In 2013, for example, several measles outbreaks occurred around the country, including large outbreaks in New York City and Texas – mainly among groups with low vaccination rates. If vaccination rates dropped to low levels nationally, diseases could become as common as they were before vaccines.
Diseases haven’t disappeared.The United States has very low rates of vaccine-preventable diseases, but this isn’t true everywhere in the world. Only one disease — smallpox — has been totally erased from the planet. Polio no longer occurs in the U.S., but it is still paralyzing children in several African countries. More than 350,000 cases of measles were reported from around the world in 2011, with outbreaks in the Pacific, Asia, Africa, and Europe. In that same year, 90% of measles cases in the U.S. were associated with cases imported from another country. Only the fact that most Americans are vaccinated against measles prevented these clusters of cases from becoming epidemics. Disease rates are low in the United States today. But if we let ourselves become vulnerable by not vaccinating, a case that could touch off an outbreak of some disease that is currently under control is just a plane ride away.