Some childhood vaccines are linked to serious side effects, but they are quite rare and do not include autism, food allergies or cancer, said a review of scientific literature Tuesday.
A host of vaccines commonly given to children under age six were the focus of the systematic review of rigorously conducted studies, published in the peer-reviewed US journal Pediatrics.
The report seeks to address a rising trend of vaccine hesitancy among parents in the North America and Europe, which has led to a resurgence of measles and whooping cough in some parts of the world.
"We found that serious adverse events that are linked to vaccines are really rare, and that when they do occur they are often not necessarily severe," said study co-author Courtney Gidengil, a pediatrician at Boston Children's Hospital and professor at Harvard Medical School.
"We think this adds to the body of evidence that the benefits really do seem to clearly outweigh the low risk of serious side effects from vaccines," she told AFP.
The study expands on a 2011 report by the Institute of Medicine that also pointed to some side effects linked to vaccines but found "few health problems are caused by or clearly associated with vaccines."
The Pediatrics report includes several vaccines that were not studied by the IOM, including those against hepatitis A, Haemophilus influenzae type b (Hib), polio, rotavirus and the pneumococcal conjugate vaccine.
Side effects of the measles, mumps and rubella (MMR) and pneumococcal vaccines included the potential for fever and seizures.
The MMR and hepatitis A vaccines were also linked to a side effect called purpura, when small blood vessels leak under the skin.
There was some evidence that immune-deficient children given the varicella vaccine against chicken pox could develop infections or have an allergic reaction.
The rotavirus vaccines, RotaTeq and Rotarix, were associated with a risk of intussusception, a condition in which one part of the intestine slides into another part.
However, the risk of this condition was rare, amounting to between 1-5 in 100,000, the researchers said.
"Clinicians who immunize children regularly may have encountered these adverse events in their practices, particularly seizures associated with fever," said an accompanying editorial by Carrie Byington, vice chair for research in the pediatrics department at the University of Utah. "Fortunately, the adverse events identified by the authors were rare and in most cases would be expected to resolve completely after the acute event."
No fatalities were found in the research, which spanned from 2010 to 2013 and included a total of 67 studies, whittled down from more than 20,000 research papers.
Each study that made the final cut had a control or comparison group, and involved vaccines approved for the US market as of 2011.
The report found insufficient evidence to link the inactivated polio vaccine to food allergies, and showed no link between childhood vaccines and the onset of leukemia.
Furthermore, its review of research backed up the IOM conclusion that the "MMR vaccine is not associated with autism," the report said.
The systematic review excluded reports to the federal Vaccine Adverse Event Reporting System, which contains complaints filed by individuals or health care professionals if they suspect a vaccine may have caused a problem with a patient's health.
"We didn't use that data because there is no comparison group out there and there is no way to really assess the validity and reliability," said co-author Margaret Maglione, a policy analyst at RAND Corporation.
The paper described vaccines as "one of the greatest public health achievements of the 20th century for their role in eradicating smallpox and controlling polio, measles, rubella, and other infectious diseases in the United States."
Gidengil said that the latest study may not be enough to change the minds of parents who are skeptical of vaccines.
"Without this work there would be a lack of transparency around this issue, so by doing this important research in a thorough and systematic way, we acknowledge that there are rare but actual side effects," she said.
"And we can document those clearly for people, which we hope will just increase some trust in the vaccine process and the trust between parents and their health care provider."
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Your newborn should get this shot even before leaving the hospital, and receive another dose at one to two months and a third at six to 18 months. The vaccine protects against an incurable, liver-infecting virus, hepatitis B, which can be passed to a baby during childbirth if the mother is infected. This virus spreads through contact with blood or other body fluids (sharing toothbrushes and utensils can put you at risk). Soreness at the site of the shot, or a slight fever, is the most common side effect, according to Gabrielle Gold-von Simson, M.D., assistant professor of pediatrics at NYU Langone Medical Center in New York.
The DTaP vaccine protects against diphtheria (a germ that can form a gray or black film in the throat), tetanus (an infection that can cause muscle spasms so strong they can break bones), and pertussis (a highly contagious disease that causes a severe, uncontrollable cough, known as whooping cough). Five vaccine doses are given to children at two months, four months, six months, 15 to 18 months and four to six years. (And boosters at age 11 or 12 and then every 10 years.) DTaP may be combined with other vaccinations to reduce the number of shots needed. "Now, it's DTaP with hepatitis B and the polio vaccine. So, it's five in one," Dr. Gold-von Simson says.
This combo shot protects against three viruses: measles (which causes high fever and a body-wide rash); mumps (which causes face pain, swelling of the salivary glands, and sometimes scrotal swelling in boys); and rubella or German measles (which can cause birth defects if the infection occurs during pregnancy). The first shot is given at 12 to 15 months of age and once again between the ages of four and six. MMR is sometimes combined with the chickenpox vaccine into one shot (brand name ProQuad). "All these different preparations are designed to reduce the amount of shots the pediatrician has to give," says Dr. Gold-von Simson.
Chickenpox, a highly contagious rash that many people remember from childhood, is caused by the varicella virus. A varicella vaccine was first licensed in 1995 and now spares future generations this itchy misery. Chickenpox infections can be especially dangerous in adults who don't have immunity from the vaccine or haven't had it in childhood, and can also lead to shingles, an extremely painful blistering rash. The shot is given to children at 12 to 15 months and again between four and six years. The vaccine can cause soreness at the site of the shot, fever, and, in some cases, a mild rash.
Haemophilus Influenza Type B (Hib)
"Haemophilus influenza type b is the bacterium that causes meningitis," says Dr. Gold-von Simson. Meningitis, an inflammation of the membranes surrounding the brain and spinal cord, is particularly dangerous for kids under the age of five. Hib vaccines are generally given at two, four, six, and 12 to 15 months of age. Depending on the vaccine used, the six-month shot may not be needed. Fever, swelling, and redness at the site of the shot are potential side effects.
Polio vaccine is "such a success," says Dr. Gold-von Simson. "Because of the vaccine, there are no more cases (of polio)." There are no more in the United States that is. The virus hasn't been eradicated worldwide, so kids still get the IPV, or inactivated polio vaccine, which is a shot containing killed virus. Polio is bad news, and can cause paralysis and even death. Children are given the IPV at two months, four months, between six to 18 months, and then again between the ages of four and six years.
Pneumococcal Conjugate (PCV)
This vaccine, known as PCV13 (brand name Prevnar), protects against 13 types of Streptococcus pneumoniae, which are bacteria that can cause all sorts of mayhem, including meningitis, pneumonia, ear infections, blood infections, and even death. A total of four shots are given to kids (at two, four, six, and 12 to 15 months of age) to protect them against the germs, known collectively as pneumococcal bacteria. The most common side effects of the vaccine include drowsiness, swelling at the site of the shot, mild fever, and irritability.
Flu vaccinations are given each year starting in the fall. The Centers for Disease Control and Prevention recommends them for kids ages six months or older, although they aren't required for school attendance. (Connecticut and New Jersey require the vaccine for attending child-care centers and preschool.) Common side effects from the vaccine include soreness, redness, or swelling at the site of the shot. Fever and aches may occur too. "If you have an egg allergy, you shouldn't have the influenza vaccine," says Dr. Gold-von Simson.
The rotavirus vaccine (RV) (brand names RotaTeq, Rotarix) is given to children at two and four months of age. (RotaTeq is also given at six months.) The vaccine protects against a virus that is the most common cause of severe diarrhea and vomiting in young kids worldwide. About 55,000 children in the U.S. were hospitalized each year due to rotavirus before the vaccine was licensed in 2006. It is not required for school attendance. The vaccine is in liquid form and given by mouth to babies. It may make them a bit more irritable and can also cause mild diarrhea or vomiting.
Kids can catch hepatitis A from sharing food or drinks or by putting contaminated food or objects in their mouths. It's a viral infection that affects the liver, and can cause a number of symptoms, including fever, tiredness, jaundice, and loss of appetite. Children ages 12 through 23 months generally get two doses of the Hep A vaccine, with a minimum interval of six months between shots. Some states require the vaccine for school attendance. Soreness where the shot was given, headache, and loss of appetite are the most common side effects of the vaccine.
Meningococcal Conjugate (MCV4)
This vaccine, known as MCV4 (brand name Menactra), protects against meningococcal bacteria, which can infect the membranes surrounding the brain and spinal cord. MCV4 is recommended for kids at 11 or 12 years of age, and anyone between ages two and 55 who is at increased risk of infection (people with certain health conditions, military recruits). Teens starting college should be vaccinated with MCV4 before going to school if they didn't previously get the shot. (Freshman living in dorms are at increased risk of infection.) A little pain at the site of the shot is the most common side effect.
Human Papillomavirus (HPV)
Human papillomavirus (HPV) vaccine (brand names Gardasil, Cervarix) is given in three doses over a six-month period, and is approved for girls between ages nine and 26. While there are over a hundred types of HPV, this vaccine protects against two sexually transmitted types that are the most common causes of cervical cancer. Gardasil also protects against two types that cause genital warts and is approved for boys between nine and 26 as well. The vaccine works only if given before an infection, so doctors recommend it for kids well before they could become sexually active. Although most states don't require HPV vaccination, many are considering mandating it for preteen girls.