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Coronavirus and COVID-19 Information: Santa Clara County and Bay Area, California

Trustworthy information about COVID-19

Getting a COVID Vaccination in the Bay Area

Currently 3 different vaccines have been approved (on an emergency basis) by the FDA for the U.S. Two - the vaccines from Pfizer/BioNTech and from Moderna - require 2 doses of the vaccine to be fully effective; the Johnson & Johnson vaccine reaches full effectiveness after just 1 dose.

At present, most people don't have a choice of which vaccine they get (these 3 offer roughly similar protection). However, people with some medical conditions (or taking some drugs) may do better with one or another version. If you think this might be the case for you, talk with your health care team.

The exception is that only one vaccine - from Pfizer/BioNTech - has been approved by the FDA for ages 12+. If looking to vaccinate anyone 12-18 years old, be sure to check whether the location has the correct vaccine available.

If you happen to miss getting the second dose of either the Pfizer/BioNTech or Moderna vaccine, you will still be somewhat protected, but not as well as you would be with that second dose. It's best to reschedule that missed appointment within 47 days of the first dose, but if you cannot get the second dose until later, definitely get it anyway.


graphic for Santa Clara County vaccine information at








Getting the vaccine - make an appointment or find a walk-in location:

Santa Clara residents can make an appointment to get the COVID vaccine at any one of several county locations using the links on this website. Some locations offer walk-in vaccinations, no appointment necessary.

Don't have internet access? Eligible residents can also make appointments for the County HealthSystem vaccine sites through the Valley Connection Call Center at 408-970-2000.  The Call Center is open Monday through Friday from 7am to 9pm and Saturday and Sunday from 8am to 4:30pm. Assistance is available in English, Spanish, Vietnamese, and multiple other languages.

For details on who is currently eligible to be vaccinated, and where, around the Bay Area, check with your healthcare provider (if you have insurance) and with your county health authority.

Stadiums, fairgrounds, community centers, churches, offices and local pharmacies are being added frequently as vaccination sites.


In the U.S., COVID vaccines are purchased with taxpayer funds, and are free - but there still might be an administration fee. (The full cost is covered for people without health insurance.)

Transportation to a vaccine location:

In Santa Clara County, many vaccination locations are accessible by free public transit (VTA).

Vaccine Booster Doses


On Sept. 24, 2021, the FDA and CDC approved booster shots for people who received the Pfizer-BioNTech vaccine and are among higher-risk groups. So far, approval is only for a 3rd dose of the Pfizer-BioNTech vaccine, at least 6 months after the second dose. For more details on who is eligible for reasons of risk or medical vulnerability, see:

What Happens After Getting a Vaccine?

Information on the side effects of the vaccine, and precautions to take:

one person pointing to recent vaccination + health care worker, from Santa Clara County Dept. of Public Health.

After getting vaccinated, sign up with the CDC's reporting system to record your reactions, and help to push our knowledge of how to treat this novel disease forward. Sign up after the first dose, for 2-part vaccines or after the 1-shot version.


Getting vaccinated now does not mean we can immediately go back to our pre-pandemic life. The hope is vaccines will save lives and keep fewer people from getting seriously ill, but they probably will not be able to stop the pandemic in its tracks quite yet. People who have been fully vaccinated (at least 14 days after their last vaccine dose) do not need to mask their faces or keep physically distance except in certain situations. (See the page in this guide for Slowing the Spread for details.) However, we are likely to need to keep taking some precautions until young children can be safely vaccinated and until worldwide infection rates are significantly lower.


New CDC infographics:


CDC guidelines on contact between households that have a mix of vaccinated and unvaccinated people

Available COVID-19 Vaccines

Three vaccines were approved for use in the U.S. :  from the drug companies Moderna, from Pfizer / BioNTech, and from Johnson & Johnson. They are very similar: 

  • Are currently approved for adults. At present Pfizer / BioNTech's vaccine is approved for people 12+; the other two for people 18+.
  • Use mRNA (messenger RNA) to cause our immune systems to build antibodies to the novel coronavirus. Because these vaccines don't include any actual viruses, they cannot cause COVID-19.

The first two from Moderna and Pfizer/BioNTech require two doses approximately a month apart (28 days for the Pfizer vaccine, 21 days for Moderna) to be fully effective. The Johnson & Johnson vaccine uses only one dose.

How Do These Vaccines Work? Are They Safe?

Most of us have a really basic idea of how vaccines work: by taking in a small dose of a relatively harmless version of a pathogen, our bodies create antibodies against that disease, so when we're exposed to infection, we are already equipped to fight it off. That's not wrong, but immunity is rather more complex. There are several different types of vaccines; depending on type and depending on the disease, each with their own limitations on how completely they can protect us and for how long.

vaccine safety image, two adults + a child, from the Santa Clara County Department of Public Health.

For a better understanding what vaccines can do for us, see:

How well our bodies resist infection - our immunity, in other words - depends on the strength of the antibodies created in our bodies and on how healthy we are overall. Active immunity (when our bodies create antibodies for ourselves) is stronger than passive immunity (when we are given antibodies from someone else) and also lasts longer. In the early days of this pandemic there was some hope that passive immunity transferred by blood plasma infusions from people who had recovered from COVID-19 would offer cures, but that turned out to be too unpredictable to be useful on a large scale.

Vaccine safety is a big concern to many in the U.S. There has been a lot of mis- and dis-information in the last decade on the topic of vaccines, especially vaccines for children. These sources will bust many of those myths:

The Centers for Disease Control and Prevention explains how they will make sure that the COVID-19 vaccines offered to the people of the U.S. are safe:

How Vaccines are Evaluated

With familiar and well-known diseases like whooping cough (pertussis) or polio, we can measure the effectiveness of a vaccine, using past case history and statistics to figure out how many people were not infected because they got the vaccine, compared to unprotected people. 

Effectiveness is impossible to calculate accurately for a new disease like the novel coronavirus. With COVID-19 the best we can do for now is measure efficacy (compare the number of cases in one group that got the vaccine, versus another control group that did not). And as one immunology textbook points out, when we look at vaccines, we are concerned with efficacy in three different areas:

  • Efficacy to prevent infection (also called sterilizing immunity)
  • Efficacy to prevent disease [getting sick and also transmitting the disease to others]
  • Efficacy to prevent severe disease

The currently-available vaccines for COVID-19 are good at the last one, and also the second - but they don't offer sterilizing immunity.

Clinical trials testing efficacy of vaccines need to be as diverse as the population they intend to help. When there's only a small number of people participating in a clinical trial, though, it's hard to have confidence that it will work on more than a narrow slice of the population. The current clinical trials for COVID-19 vaccines being considered in the U.S. are paying attention to that problem; and the National Institutes of Health's All of US program aims to recruit larger and much more diverse groups of people to participate in all kinds of clinical trials, to avoid further bias in healthcare.

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