Info about the chickenpox vaccine-
The big question in everyone's mind is how long the vaccine lasts, and Merck doesn't have any more answers than anyone else. In its handout on the drug, Merck admits 'the duration of protection from varicella infection after vaccination with VARIVAX is unknown.' Although those in favour of the vaccine argue that children show evidence of antibodies for at least six years (J Infect Dis, January 1994), and that booster shots can always be given, the vaccine doesn't work as well among adults, conferring only 70 per cent protection (Rev Infect Dis, 1991;13 Suppl 11: 5957-9).
However, all that any scientific study can do is to measure antibody levels, which may not be a true picture of whether someone is adequately protected. In one study of 14 healthy children who'd contracted chickenpox naturally, three lost any evidence of antibodies or immunity (Pediatr Infect Dis J, 1991; 10: 569-75). In another study of 21 pregnant women, four developed the disease even though they'd had prior evidence of antibodies from naturally occurring chickenpox. The study concluded that thee criteria for determining immunity from the chickenpox zoster virus 'remain ill-defined' (J Infect Dis,1994;170: 991-5).
We also have no idea at what point children require boosters so that a repeat of the US situation with measles doesn't occur. In the late 1980s and early 1990s, epidemics of measles occurred among college-age teenagers and young adults, most of whom had been vaccinated against measles as children because the vaccine wore off. Furthermore, it's thought that even immunized patients require reexposure to natural chickenpox or reimmunization in order to boost long-term immunity. Although it is planned that this vaccine will be given with the measles-mumps-rubella triple jab, it has been shown not to work as well when given at the same time as the Hib vaccine.
The problem with waning immunity, of course, is that giving this vaccine may create a population of adults at greater risk of serious illness than they would have been if they'd got chickenpox as children. It could turn what is largely a benign childhood disease into a source of major illness and hospitalization. Indeed, in one study of the vaccine, the number of cases of chickenpox in adults did increase (cited in JAMA, June 22/29,1994).
Another concern is the effect of injecting into one-year-old babies and children a live virus which has a tendency to lie latent in the nervous system and reactivate many years later. A majority of patients who have had chickenpox as children may go on to develop herpes zoster, commonly known as shingles, later in life. This condition causes painful and highly sensitive blisters on the skin along the nerves infected by the virus, often on only one side of the body. The severe pain may last from two to five weeks and in older patients, this jabbing pain can go on for several months.
There is some evidence that the live chickenpox vaccine can incubate in the body, causing shingles in later life. At least three cases of shingles have been reported in healthy children given the vaccine (J Infect Dis, May 1989), and one in a healthy adult (J Infect Dis, September 1989). It's also developed in children with leukemia (The Lancet, May 28, 1994). This, of course, means that the vaccine cannot accomplish its stated aim - to wipe out the zoster virus altogether. In one small study, 11 children developing a rash after vaccination were found to have the shingles virus (Pediatrics, May 1991).
We also don't know whether the live vaccine virus is itself contagious. According to Merck's information sheet: 'Individuals vaccinated with VARIVAX may potentially be capable of transmitting the vaccine virus to close contacts.' Perhaps the greatest worry is the likelihood that future babies will be more susceptible to chickenpox once this generation of vaccinated girls is unable to pass on maternal immunity. With measles in 1990, the largest increases in the incidence rates of the disease occurred among babies under one (137 per cent) and adults over 25 (130 per cent) (JAMA, June 26,1991).
Although many studies demonstrate a very high take-up rate among children - 70-90 per cent or more demonstrate antibodies to the disease - there is also a high incidence of what has been termed 'breakthrough cases' - that is, vaccinated children who have gone on to develop chickenpox. In one study, one-fifth of vaccinated children went on to develop chickenpox, although it was a more mild form of the illness. In another study, conducted by Merck itself, 12 per cent of 3303 children caught chickenpox when exposed to it at home (Pediatrics, May 1991). As for adults, 27 per cent of a Merck-studied group which received two doses of VARIVAX developed chickenpox when exposed to it in the household over two years.
Much has been made of the minor side effects of this jab. Merck says that about a fifth have swelling, rash or the like at the injection site, 15 per cent have a fever of 30 degrees C or higher, and about 7 per cent have a chickenpox rash at the injection site or locally. Otherwise, 21 per cent of patients reported an adverse reaction, including (in decreasing order of frequency): upper respiratory illness, cough, irritability/ nervousness, fatigue, disturbed sleep, diarrhea, lost of appetite, vomiting, ear infection, diaper rash or contact rash, headache, teething, malaise, abdominal pain, nausea, eye complaints, chills, enlargement of the lymph nodes, myalgia, lower respiratory illness, allergic reactions (including allergic rash and hives), stiff neck, heat rash, prickly heat, arthralgia, eczema, dry skin or dermatitis, conspitation and itching. Adults have reported similar side effects, albeit with far less frequency.
However, what doctors don't tell you is that around 1 in every 100 of children vaccinated with VARIVAX have gone on to develop pneumonia, and some one in 1000 children have febrile seizures. In one study of 3303 children, one 16-month-old baby was hospitalized with rash, fever, swelling of the right knee 16 days after the vaccine (Pediatrics, May 1991), and one adult developed a severe kidney inflammation after the jab (Clin Infect Dis,1993;17:1079).
Furthermore, these reactions, including fever and rash, can happen at any point for six weeks after vaccination and last for six days or more - which would tend to rebuke the notion that parents are going to save time off work by vaccination (Pediatrics, Sept 1991).