Coronavirus Q&A

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Useful Information

Dr. Sunny Pak from the San Francisco Chinatown Public Health Center answers additional CoVID-19 vaccine questions in Cantonese

Question: Which vaccine is the best? I know they say just take whatever vaccine is available, and the % of effectiveness are slightly different, but is there a best choice between Pfizer, Moderna, and Johnson & Johnson? I heard that the Moderna vaccine is better for APIs but that the Pfizer is better for seniors – what is the difference and which one should I pick?

Question: Will the vaccine give me COVID-19? If others in my family haven’t gotten the vaccine, won’t I get them sick? Can I still pass on COVID-19 to other people after getting vaccinated?

Question: What if I have a preexisting condition like heart disease, kidney disease, or diabetes, how will the vaccine affect me? Will it make things worse? Can I take the vaccine if I am on medication? Will the vaccine interfere if I have ongoing diseases/allergies? (high-blood pressure, anemic, diabetic etc.)

Question: Where can I get a vaccine in San Francisco? Why is it so challenging to get a vaccine? Do I need medical insurance? Will the vaccination ask me if I have a labor certificate?

Frequently asked Vaccine Q&A
Who can get vaccinated now? Click on Vaccine Eligibility Expansion to Persons Under 65 with Qualifying Conditions (San Francisco)
(3/15/2021) As 27% of San Franciscan adults have received at least one dose of vaccines, the City has expanded its vaccine eligibility requirements to include individuals who:
  • Are age 16 to 64 at high risk for severe COVID-19 due to one or more health conditions
  • Are age 16 to 64 with disabilities
  • Live or work in high-risk congregate care facilities, including correctional facilities, homeless shelters, and other congregate residential care/treatment facilities
  • Are experiencing homelessness

Eligible people can schedule a vaccination appointment through the state’s MyTurn system, county vaccine websites, and some health care providers.

Do I need to prove if I have qualifying conditions in order to get the vaccine?
Verification policy varies across counties and providers at this time.

But for UCSF and other publicly-run sites in San Francisco, they follow State and City guidance that relies on attestation and will not require verification.

For those UCSF patients who need proof of eligibility for health conditions, we have a template letter in MyChart (the electronic medical record) that clinicians can type in.

I am worried about getting the vaccine because I heard the side effects are very severe
From the CDC website:

You may have some side effects, which are normal signs that your body is building protection. Common side effects are pain, redness, and swelling in the arm where you received the shot, as well as tiredness, headache, muscle pain, chills, fever, and nausea throughout the rest of the body. These side effects could affect your ability to do daily activities, but they should go away in a few days. Learn more about what to expect after getting a COVID-19 vaccine. Some people have no side effects.

What if I have a preexisting condition like heart disease, kidney disease, or diabetes, how will the vaccine affect me? Will it make things worse?
From the CDC website:

People with underlying medical conditions can receive a COVID-19 vaccine as long as they have not had an immediate or severe allergic reaction to a COVID-19 vaccine or to any of the ingredients in the vaccine. Learn more about vaccination considerations for people with underlying medical conditions. Vaccination is an important consideration for adults of any age with certain underlying medical conditions because they are at increased risk for severe illness from COVID-19.

Specifically, how do the vaccines differ from each other?
Vaccine manufacturers report information from clinical trials, including demographics and underlying medical conditions of people who participated in COVID-19 vaccine trials. You can find additional information on COVID-19 vaccine clinical trials at, a database of privately and publicly funded clinical studies conducted around the world.

Information on Pfizer/BioNTech COVID-19 Vaccine:

Information on Moderna COVID-19 vaccine

Information on Johnson & Johnson (Janssen) COVID-19 vaccine

Will the mutations of the virus mean Pifzer, Moderna won’t be as effective?
From STAT:
Both the Moderna and Pfizer-BioNTech vaccines finished clinical trials before the emergence of B.1.351 and other variants of concern, so there are no clinical data for how they defend against the newer iterations of the virus. But in their trials, both were shown to be greater than 90% efficacious at preventing symptomatic Covid-19, so some experts have argued that even if they lose some of their oomph against particular variants, they have enough cushion to remain highly protective.

Novavax and J&J trials reported drops in efficacy in against the variant. Moderna, last month reported that its vaccine was also less potent against B.1.351 in lab experiments, but said it believed the levels of antibodies generated should still be protective.

From CDC:
Preliminary results from the United Kingdom demonstrate that vaccination with two doses of Pfizer-BioNTech COVID-19 vaccine was highly effective (85–86%) against SARS-CoV-2 infection and symptomatic COVID-19 during a period when B.1.1.7 was the predominant circulating strain. Similarly, high Pfizer-BioNTech vaccine effectiveness (92%) against infection was observed in Israel in the context of multiple circulating strains, with the proportion of cases due to the B.1.1.7 variant increasing to 80% towards the end of the evaluation period. Preliminary data suggest that the Janssen COVID-19 vaccine may have reduced overall efficacy against the B.1.351 variant. In the United States, efficacy was 74% and in Brazil (where ~69% of infections were due to P.2) efficacy was 66%, but in South Africa (~where 95% of infections were due to B.1.351) efficacy was 52%. However, Janssen vaccine efficacy against severe or critical disease was high and similar across sites (73–82%) .

The Pfizer and Moderna vaccines are made with a piece of genetic code called messenger RNA that tells the body how to make some harmless copies of the spike protein that train immune cells. To update the vaccine, they can simply swap out the original genetic code with mRNA for the mutated spike protein.

Can a person who has tested positive get vaccinated?
The CDC also addresses this question in a post titled, "I've already had COVID, should I still get vaccinated?"

The answer, the CDC writes: "Yes, due to the severe health risks associated with COVID-19 and the fact that reinfection with COVID-19 is possible, you should be vaccinated regardless of whether you already had a COVID-19 infection."
However, the CDC adds the caveat that if someone was treated for COVID-19 symptoms with monoclonal antibodies or convalescent plasma, they should wait 90 days before getting a COVID-19 vaccine. If you’re unsure what treatment you received, the CDC urges you to consult your doctor. (Having those synthetic antibodies or having convalescent plasma can actually reduce the efficacy of the vaccine because it basically stops the vaccine from working before it gets started.)

Is the vaccine only effective for a few months?
We don't know how long protection lasts for those who were vaccinated.
Experts are working to learn more about both natural immunity and vaccine-induced immunity. CDC will keep the public informed as new evidence becomes available. COVID-19 has caused very serious illness and death for a lot of people. If you get COVID-19, you also risk giving it to loved ones who may get very sick. Getting a COVID-19 vaccine is a safer choice.

Cancer related Vaccine Q&A
My WBC has dropped recently to 3000 only, not sure which of my previous cancers is recurring. With my poor health condition & compromised immunity, can I still take the Covid vaccine?
Dr. Ko: Yes, it is still safe for cancer patients to receive the vaccine, including those with compromised immune systems (i.e. from receiving chemotherapy).

I am undergoing chemo, can I take the vaccine now or wait till the treatment is finished?
Dr. Ko: Yes, it is still safe for cancer patients to receive the vaccine, including those with compromised immune systems (i.e. from receiving chemotherapy). In general, we recommend trying to separate the timing of your vaccine from the day you’re receiving chemotherapy, by at least a few days.

For people in stage 4 cancer, should they take the vaccine?
Dr. Ko: Yes, it is still safe for cancer patients to receive the vaccine, including those with compromised immune systems (i.e. from receiving chemotherapy).

I had a liver transplant 3 years ago, and am taking immunosuppressants. Should I take the vaccine? Does it matter which type?
Dr. Ko: Yes, post-liver transplant patients are recommended to take the vaccine. Moderna and Pfizer would be good choices as they are mRNA vaccines (i.e. do not contain attenuated virus).



舊金山唐人街公共衛生中心的白幹榮醫學博士回答了CoVID-19疫苗的問題 (廣東話)

視頻 #1
問題: 目前市面有輝瑞、莫德納和強生這三種疫苗,我們聽聞莫德納疫苗對亞太裔特別有效,而輝瑞對長者又較好,到底分別在那裡?哪種疫苗更好?我們應該如何選擇呢?

視頻 #2
問題: 接種疫苗會否令我們感染新型冠狀病毒? 如果我的家庭成員未有接種疫苗,我會否令他們生病? 我接種疫苗後,是否仍有機會將新型冠狀病毒傳播給其他人?

視頻 #3
問題: 如果我有先已存在的健康狀況,或者是長期病患,例如心臟病、腎病或糖尿病,又或者有高血壓,貧血等等,我是否可以接種疫苗?疫苗對我是否會有什麼負面影響?如果我正服藥,是否會有過敏現象?

問題: 我可以在三藩市那裏接種疫苗?為什麼預約接種疫苗如此困難?我是否需有醫療健保?接種疫苗是否會詢問我有沒有勞工證呢?


(3/15/2021) 由於27%的舊金山成人已經接種了至少一劑疫苗,本市也已將接種疫苗資格的要求擴大至包括以下人員:
  • 年齡在16至64歲之間,並由於一種或多種健康狀況而有感染嚴重新冠肺炎(COVID-19)的高風險
  • 年齡在16歲至64歲之間,並有殘疾
  • 在高風險的集體護理設施中生活或工作,包括懲教所,無家可歸者之收容所與其他集體住宿護理/治療設施
  • 無家可歸人士


加州大學舊金山分校病人如果需要有健康狀況的證明,我們在MyChart 網站(電子病歷)中有一信件範本,可供臨床醫生填寫做證明。

摘自 “疾病預防控制中心” (CDC) 網頁:

摘自 “疾病預防控制中心” (CDC) 網頁:
患有慢性病的人士只要對新冠肺炎疫苗或疫苗中的任何成分沒有即時或嚴重的過敏反應,是可以接種疫苗。要瞭解更多有關慢性病患者接種疫苗需要注意的事項。 對於患上某些慢性病的成年人,不論年齡,考慮接種疫苗都很重要,因為新冠肺炎會令他們生重病的風險增加。

疫苗製造商會匯報來自臨床試驗的資訊,包括參與新冠肺炎疫苗試驗人士的統計資料和潛在的慢性病。 你可以在clinicaltrials.gov網站上找到更多有關疫苗臨床試驗之資訊,這是在全球私人資助和公共基金的臨床研究之數據庫。

關于輝瑞(Pfizer) /復必泰(BioNTech)新冠肺炎疫苗之資訊:

有關莫德納(Moderna) 新冠肺炎疫苗之資訊


摘自“STAT” 網頁:


摘自 “疾病預防控制中心”( CDC ) 網頁:

輝瑞/復必泰和莫德納疫苗是用一種稱為 “信使核糖核酸” (messenger RNA)的遺傳密碼製成,該密碼告訴人體如何製作一些無害的刺突蛋白,讓其 訓練產生免疫細胞。如果需要更新疫苗,他們可以簡單地將含“信使核糖核酸” (mRNA)的遺傳密碼更換為已變異的刺突蛋白即可。


不過,疾病預防控制中心補充,如果已使用過單克隆抗體或康復期血漿去治療新冠肺炎徵狀,他們則應該先等90天才去接種疫苗。 如果不確定已接受哪種治療,疾病預防控制中心(CDC)主張你諮詢醫生。 (事實上,體內如果含有這些合成抗體或康復性血漿是會降低疫苗的功效的,因為它會在疫苗開始產生效用之前停止其工作。)


我的白血球最近下降到僅有3000,現未確定我以前哪種癌症正在復發。 由於我不良之健康狀況,且免疫力受損,我仍適宜接種新冠肺炎(Covid)疫苗嗎?



我三年前接受了肝移植手術,現正在服用免疫抑製劑。 我應該接種疫苗嗎? 接種哪種類型會有關係嗎?
Ko醫生:可以。我們建議曾接受肝移植者接種疫苗。 Moderna與Pfizer都是信使核糖核酸(mRNA)疫苗,不含滅活病毒,會是適當的選擇。