Ask the Doctors: Vaccine could be fast-tracked

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Q: 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?

A: 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.

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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.

Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health. Send your questions to, 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.


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