A person who is inoculated with COVID-19 vaccine can still become infected, so there is still a need to observe strict social distancing and wear face masks until the development of herd immunity, according to a Thai post-doctorate researcher at the University of Chicago.

The researcher, Dr. Siriruk Changrob, has received two doses of the Pfizer-BioNTech vaccine. She talked to Thai PBS, in an online interview, about her condition following vaccination and offered some advice.

She received the first injection about 20 days ago. She then showed up for the second injection, as appointed, and was asked by the nurse about any side effects from the first jab and whether she had tested positive for the virus in the preceding 90 days.

After the second injection, the nurse congratulated her for having received her two doses of the vaccine, as required, and attached an “I got my COVID-19 vaccine” sticker to her employment ID card, which might be necessary when travelling, said Dr. Siriruk.

She said she didn’t feel anything until about eight hours after the second injection, when she started to feel feverish and some pain at the injection site, adding that all her colleagues warned her that the post second injection symptoms would be more painful.


She explained that the Pfizer vaccine requires two doses, to achieve the desired efficacy, and the first and second injections must be at least 21 days apart.

She also recommended that anyone who is not sure that they can get the second injection, within the set timeframe, not get the first one.

She also said that anyone who requires daily medication to treat other ailments should consult their doctor before being vaccinated, to ensure that the efficacy of the vaccine will not be affected by that medication.

The general post-vaccination symptoms include a fever, headache, muscle pain and shivering, she said, adding that these are positive signs that the body is developing an immunity

Taking medication to prevent the onset of a fever after vaccination is not recommended, Dr. Siriruk said, adding that the vaccine only protects a person from developing symptoms and does not protect a person from becoming infected by the virus. As such, there remains a need to maintain social distancing, to wear face masks and to regularly wash hands, until 60% of the population have developed herd immunity.