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Q. I had an egg allergy when I was a kid, around 5-6 years old. Now I’m 33 and no longer seem to have any reaction to eggs. I would like to get a flu shot, but I’ve been told I need to be sure I don’t have an egg allergy. I eat eggs every morning and don’t notice any reaction, so I don’t think I’m allergic anymore. Can I just get the flu shot? What do you suggest?

A. If you are tolerating eggs daily without symptoms, you are no longer allergic to eggs. If you do not have any skin, stomach, swallowing, throat, or breathing symptoms related to eating eggs; then you do not have to worry about egg allergy. You should get the influenza vaccine annually, and you do not need any special precautions or monitoring. 

Q. I thought the flu vaccine changed every year, but my nurse looked at this year’s flu vaccine and found it has H1N1 in it. Isn’t that the same as swine flu?

A. Your nurse is right! The terminology is a little confusing, so here’s a refresher: H1N1 is a subtype of Influenza A that has caused roughly half of all human flu infections we’ve seen in the past several years.

H1N1 viruses are identified by two surface proteins: Hemagglutinin (H) and Neuramidase (N). The strains H1, 2 and 3, and N1 and 2 are found in people – a lot more strains are found in birds and pigs, and can be spread to humans. If a sufficient genetic shift occurs in an animal virus strain, it can then be transmitted person to person.

Scientists closely monitor the strains infecting humans as well as animals, since crossover to humans may signal the next pandemic influenza.

Yes, the human influenza strains do shift from year to year, but it is very rare that all three strains in an influenza vaccine change in a single year. Therefore, you will see repeating strains if you watch the vaccines' contents.

People need a yearly influenza vaccine for two reasons: the vaccines usually contain new strains each year, and immunity to influenza decreases over time. The yearly vaccine helps keep your immunity strong and ensures that you have resistance to the strains scientists have identified as important for the year.

Q. My 4 year-old son recently had anaphylaxis after the following vaccinations were given at the same time: chickenpox, DTP, polio, and MMR. Immediately after these immunizations in our pediatrician's office, he complained of his throat hurting, was sneezing, drooling, threw up and had red, itchy skin and trouble breathing. He was taken by ambulance to the ER, and treated with shots including epinephrine. In the past, he has had drooling and vomiting after eating a piece of protein chocolate bar and when taking his gummy vitamins, and complained of his throat hurting after eating marshmallows. My son doesn't have any hay fever, and we don't have a family history of allergies. Do you have any idea what could be causing these reactions?

A. Based on the information you've provided, your child's reactions may be related to gelatin, which is added as a stabilizer to some vaccines and is found in both the MMR (measles-mumps-rubella) and chickenpox (varicella) vaccines. Yellow fever vaccine and rabies vaccine also contain gelatin, but are not part of the routine childhood vaccination schedule. 

The foods you list also frequently contain gelatin.

Neomycin, an antibiotic, is another ingredient in some vaccines which can be related to allergic reactions; it can also result in a reaction if used with topical application (as in "triple antibiotic" antibacterial skin creams, sold over-the-counter). 

Your allergist can evaluate the possibility of a gelatin (or other) allergy and perform testing on your child to confirm. Given the circumstances, any further vaccinations should be held - and foods containing gelatin avoided - until the exact cause of reactions has been determined.

Q. I am a 66 year-old man who was recently discharged from the hospital after a prolonged and resistant bout of pneumonia. After seeing an allergy/immunology doctor for an evaluation of a possible immune deficiency problem, I had some lab studies done. A certain test called gamma globulin came back in the low normal range, but some of the other tests were not quite normal. The allergist recommended that I have a Pneumovax (pneumococcal vaccine) and a tetanus/diptheria/pertussis vaccination and then have some repeat blood tests. Is it really necessary to have both of these vaccines? How do they help to identify if I have an immune problem?

A. Someone with an immune deficiency is very likely to have low normal or even normal gamma globulin levels but still have an inability to make antibodies to specific organisms such as pneumococcus (a bacteria which can cause pneumonia).

The blood work you had taken likely showed your allergist that you lacked proper antibodies to specifically fight pneumococcal diseases and that you lacked protection against tetanus and/or diphtheria. The absence of these antibodies does not in itself mean that you have an immune problem. You may have lost the immunity from the diphtheria/tetanus/pertussis that you had as a child, and may simply not have been exposed to many of the pneumococcal organisms that were tested in the blood.

However, you do need protection against all these organisms – that's a standard recommendation for all adults over 65! Receiving the vaccines your physician has recommended will likely give you that protection. Repeating the blood tests 4 weeks afer the vaccinations will help your allergist know if your immune system is functioning properly. You really need both vaccinations for protection and to gain necessary information about your immune system. If your body shows an inadequate response to these vaccines, further immune studies and treatment, possibly long-term, may be required.

These vaccines can be administered at the same time. I would suggest that you follow your allergist's advice and obtain the vaccines and then the blood tests 4 weeks later.