Dear Doctor: I just read that a coronavirus vaccine won’t be ready until at least next year. How do vaccines work? And why do they take so long to make?

Dear Reader: When measured against the catastrophe of the current pandemic, the estimate of 12 to 18 months to develop and launch a coronavirus vaccine seems like an eternity. But, believe it or not, the proposed timetable is actually extremely fast.

A vaccine is basically a lesson plan that teaches the body how to recognize and eliminate a specific pathogen. It works by introducing the immune system to molecules known as antigens, which are the distinctive sugars and proteins that dot the outer surface of a bacterium or virus. The immune system reacts by sending antibodies to disable or destroy the pathogen. But matching the correct antibody to a brand-new pathogen takes time. So does producing enough antibodies to deal with all of the invaders.

A vaccine gives the body a head start. It presents the immune system with either a harmless form of a virus or bacterium, or with bits of antigens. Each will prompt the immune system to produce the antibodies it needs to attack that particular pathogen. The next time that unique antigen signature is detected, the immune system is ready and able to attack before the pathogen has time to make you sick.

Vaccines can take up to 10 years to develop. That’s due to the multiple phases of rigorous testing it takes to make sure a vaccine is not only effective, but also safe. It begins with work in animal models to understand how both the virus and the vaccine behave in the body. The next step is a Phase I trial, in which the vaccine’s efficacy is tested in a small group of healthy volunteers. This typically takes a year or two, but that may be scaled back to three months for a COVID-19 vaccine.

A larger Phase II trial, which further evaluates the vaccine and involves the use of placebos, usually takes two to three years. For the current vaccine, this may be shortened to eight months.

In Phase III, which also includes placebos, the vaccine is tested on thousands, or tens of thousands, of volunteers. Again, the typical timeline of two to four years is expected to be significantly shortened.

The next step is regulatory review of the clinical process, followed by production and distribution, each of which also take time. Post-approval studies are used to monitor how effective the vaccine is in real-world conditions.

Thanks to previous research into other types of coronaviruses, including those that caused the SARS and MERS outbreaks, scientists have a bit of a head start. They also are using a new and faster technique to develop the vaccine, based on genetic information known as messenger RNA. This has all led to the mid-March launch of a Phase I trial with 45 volunteers at the Kaiser Permanente Washington Health Research Institute in Seattle. It’s a significant first step in what will be a challenging and closely watched process.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Our 8-year-old grandson is coming from Atlanta to spend the summer with us in Idaho. He has asthma, and our daughter has mentioned that my husband and I have to become familiar with his “asthma action plan.” What is that? How should we prepare?

Dear Reader: An asthma action plan is a detailed roadmap for how to manage the disease, including medications and methods for preventing and controlling asthma attacks. It’s necessary because asthma, which is a chronic respiratory disease, is both complex and serious. It can cause symptoms that change not only from day to day but from minute to minute.

For most of us, the act of breathing is effortless. But people living with asthma can never take their next easy breath for granted. The airways of someone who has asthma can suddenly become inflamed and swollen, which makes it difficult to inhale and exhale. This type of chronic inflammation puts their airways on perpetual high alert and makes the tissues liable to overreact to a range of stimuli. These are known as triggers and include dust, pollution, mold, perfumes, smoke, pet dander and other allergens, as well as exertion and even certain weather conditions. Any of these triggers can cause asthma symptoms, which include a wheezing sound when someone breathes, shallow and rapid breathing, sustained coughing fits, labored breathing and weakness or exhaustion.

During an asthma attack, or flare-up, the airways become swollen enough that it becomes very difficult, or even impossible, to breathe. In addition, the groups of muscles that usually help with breathing will tighten up, making getting enough air even more challenging.

The disease is managed with two types of medications -- controllers and relievers. Controllers are typically corticosteroids delivered via an aerosol, which is inhaled. They are used in the day-to-day management of asthma to reduce chronic inflammation, decrease mucus production and relax the bands of muscles around the airways. People with mild asthma may find that this treatment is sufficient to keep the disease under control. Relievers are medications to be used when an asthma attack occurs. They work by swiftly opening up the airways and relaxing the muscles, which either stops the attack or reduces its severity.

Because asthma is both unpredictable and potentially dangerous, it’s important to plan ahead for all eventualities. That’s where the asthma action plan comes into play. It’s a written set of instructions that detail every aspect of an individual’s asthma treatment. This includes potential triggers for an asthma attack, which medications to take, their dosages, their timing and what to do in an emergency. In addition to being familiar with this plan, be sure your local pharmacy has your grandson’s asthma prescriptions on file, and that they include enough refills to last his entire visit. It’s also wise to line up local medical help, in case it is needed.

Some schools and recreational programs require a written asthma action plan on file before allowing a child to attend, so if your grandson will be taking part in any organized activities, be prepared to share the document with them.

Ask your daughter to send you a copy of your grandson’s action plan before he arrives. This will allow you to familiarize yourself with the specifics, and ask any questions you may have well in advance. Or you can find a variety of printable or electronic forms at cdc.gov/asthma/actionplan.html.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I just read your column about bone density tests and want to know your thoughts on medications for osteoporosis. Is it better to take calcium and vitamin D and engage in exercise or to risk the medications’ side effects?

Dear Reader: Yours is one of a number of letters we received about treatment for osteoporosis. It’s a subject of great importance to all women, particularly as they reach perimenopause and menopause. The increased risk of osteoporosis at that time of life is due to the drop in estrogen production by the ovaries. Estrogen plays a key role in the ongoing cycle of bone deposit and bone loss and keeps the balance in favor of bone strength. As estrogen levels drop, bone loss speeds up. That’s why the bone density tests we wrote about recently are necessary. They give each woman an idea of the changes her skeleton is undergoing and point to the appropriate treatment.

As a reminder, bone density test results include a scale known as a T-score, which is a comparison to the bone density of a healthy 30-year-old adult. The lower the number in someone’s T-score, the lower their bone density. A T-score of -1 and above is considered to be normal. Scores of -1 to -2.4 equal low bone density, also known as osteopenia. The tipping point into osteoporosis is a score of -2.5 and lower. (Because the scores are rendered in negative numbers, the larger numbers actually equal a lower score.) Guidelines suggest that when someone’s T-score indicates osteoporosis, a class of medications known as bisphosphonates should be considered. They work by inhibiting the breakdown of minerals, including calcium, which help give bone its strength.

Several readers mentioned concerns about the potential side effects of these medications, which have made news in recent years. Bisphosphonates are available in pill form and as an IV infusion. Side effects of both forms of this medication can include pain in the bones, muscles and joints. People who take the drug in tablet form have reported difficulty swallowing, nausea, heartburn, irritation to the esophagus and gastric ulcer. A condition known as osteonecrosis of the jaw, in which the jaw bone becomes exposed and fails to heal properly, has been reported in some cases. However, this is rare -- we’ve never seen this in our own practices -- and research suggests it’s more common among patients receiving high doses of IV bisphosphonates. We have many patients on bisphosphonates, and in our experience, they are generally very well-tolerated.

To decide what’s right for you, we think you should begin by sharing your concerns about these medications with your doctor. Your T-score, along with your medical history, will help guide the direction your treatment should take.

Bisphosphonates are typically prescribed along with calcium and vitamin D, both of which help to preserve and protect bones. We also recommend that our patients engage in weight-bearing and high-impact exercise, which has been shown to strengthen and preserve bone. Be sure to check with your doctor for guidance on the specific exercise and intensity level that’s right for your specific needs.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)