HOW SOME ARE REACTING TO VACCINES

As coronavirus vaccines are rolled out across the world, a growing band of recipients are complaining of being flattened by side effects, especially after a second dose. Recipients describe symptoms from fever to fatigue that are more profound than the jolt some get from a seasonal flu shot. Although the post-vaccination malaise is generally innocuous and fades after a day or two, some hospitals and medical centers are staggering immunizations of health workers to avoid a brief cluster of absenteeism.

1. What reactions can occur?

Typical symptoms include a sore arm, usually localized to the area the inoculation was given, and systemic symptoms, such as a mild fever or elevated temperature, headache and muscle aches. Some studies have found younger adults report localized and systemic reactions more frequently than people over 65 years old. A type of skin eruption, known as a morbilliform rash, was described in a 30-year-old male health care worker two days after his second vaccine. The rash, which covered most of his back, cleared up after a day.

2. Are they cause for concern?

Reactions may be unpleasant, but they are usually short-lived and far less serious than what’s inflicted by a natural infection. Vaccines are tested extensively for safety before release. Once in large-scale use, they are monitored in “postmarketing” surveillance systems for unexpected or rare reactions that are too uncommon to have been picked up in clinical trials. These products wouldn’t be licensed if they were likely to be severe or longlasting.

3. What causes reactions to vaccines?

Vaccines are designed to mimic a natural infection without the full-blown disease, thus generating immunity. Reactions result from the immune system’s response to the key component: an antigen that resembles whatever bug it’s designed to fight. Normally, when the body encounters a bacteria, virus or some other foe, immune defenses seek to neutralize and destroy it. Chemicals that attract cells to kill the invader are released in a process that can raise the body temperature, said Peter English, a consultant in communicable disease control in the U.K. A vast army of T cells and B cells are recruited to generate “memory” of the foe and how to thwart it.“in learning to recognize the pathogen, the body goes through the same immune reactions as it would if it had met the pathogen for real, producing many of the same reactions,” English said.

4. What else can cause a reaction?

Vaccines may also contain components that can induce a reaction, or enhance the immune response to the vaccine antigens, English said. Coronavirus vaccines may also include:

Preservatives to prevent the vaccine from spoiling.

Microscopic bubbles of lipids or fatty materials that contain the genetic material for MRNA vaccines (manufactured by Moderna Inc., Pfizer Inc. and Biontech SE) to instruct cells to produce SARSCOV-2 antigens.

Harmless viruses to smuggle genetic material into the cells to instruct them to produce SARSCOV-2 antigens.

Harmless chemical “adjuvants” designed to increase the immune response to the antigens.

5. Why are reactions to the second dose worse?

It takes time for the immune system to hone its response to a new pathogen. Immune memory cells are programmed such that when they encounter an invader a second time they are primed to respond faster and more vigorously.