# Does the 4th booster ever cause a positive test? **URL:** \ **Category:** The Quarantine Zone\ **Tags:** covid-quarantine\ **Created:** [April 4, 2022, 1:53pm UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241 "2022-04-04T13:53:37Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [April 4, 2022, 1:53pm UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/1 "2022-04-04T13:53:37Z")
We got the (2nd) Moderna booster Friday. Today, Monday, Mrs. CC, older and immunocompromised, tested positive with a home test. Could that result be from getting a booster? ---
**Author:** ![Smapti](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/smapti/32/17938_2.png) [@Smapti](https://boards.straightdope.com/u/Smapti)\ **Post date:** [April 4, 2022, 1:57pm UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/2 "2022-04-04T13:57:02Z")
I’m not a doctor nor do I play one on TV, but I don’t see how an mRNA vaccine could cause a positive result on an antigen test. ---
**Author:** ![SanVito](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sanvito/32/2805_2.png) [@SanVito](https://boards.straightdope.com/u/SanVito)\ **Post date:** [April 4, 2022, 1:59pm UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/3 "2022-04-04T13:59:49Z")
I agree, I’m afraid it sounds like Mrs CC has Covid. Probably worth getting a PCR test to be certain. Hopefully she only suffers a mild dose. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [April 4, 2022, 2:56pm UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/4 "2022-04-04T14:56:07Z")
> [@SanVito](#): > > I agree, I’m afraid it sounds like Mrs CC has Covid. Or a false positive; the newer lateral flow (‘at home’) tests have much better specificity but earlier ones were pretty poor in that regard, so it is always advisable to use multiple tests or a rtPCR (lab test) if unsure. Stranger ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [April 4, 2022, 3:02pm UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/5 "2022-04-04T15:02:47Z")
No, it is impossible for there to be any causal connection between an mRNA vaccination and a positive antigen test. See here for the structure of the virus: [SARS-CoV-2 - Wikipedia](https://en.wikipedia.org/wiki/Severe_acute_respiratory_syndrome_coronavirus_2#Structure) The mRNA vaccines code only for the S (spike) part of the virus, not the entire virus. The antigen tests detect the N (nucleocapsid) part of the virus, see here for example with reference to the Abbot test: [Multidisciplinary assessment of the Abbott BinaxNOW SARS-CoV-2 point-of-care antigen test in the context of emerging viral variants and self-administration | Scientific Reports](https://www.nature.com/articles/s41598-021-94055-1) So the antigen test is detecting a part of the virus that is just not present in the mRNA vaccine. There is certainly some non-zero false positive rate, as with any test. But there is no causal connection between false positives and mRNA vaccination. Mrs CC should provisionally assume that she has COVID, take precautions and seek whatever medical care is appropriate given her condition, and get a PCR test to confirm. ---
**Author:** ![BippityBoppityBoo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bippityboppityboo/32/5745_2.png) [@BippityBoppityBoo](https://boards.straightdope.com/u/BippityBoppityBoo)\ **Post date:** [April 4, 2022, 8:42pm UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/6 "2022-04-04T20:42:19Z")
> [@CC](#): > > Today, Monday, Mrs. CC, older and immunocompromised, tested positive with a home test. From the CDC site [what to do if test positive]:… If you receive a positive test result, you should - Stay home for at least 5 days and [isolate](https://www.cdc.gov/coronavirus/2019-ncov/your-health/quarantine-isolation.html) from others in your home. - Tell your [close contacts](https://www.cdc.gov/coronavirus/2019-ncov/daily-life-coping/tell-your-contacts.html). - Wear a [well-fitting mask](https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/types-of-masks.html) when around others. If available, a N95 or KN95 respirator is recommended. - Watch for [symptoms](https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symptoms.html). If you have any [emergency warning signs](https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symptoms.html), seek emergency care immediately. - Tell your healthcare provider. Contact them as soon as possible if: - Your symptoms get worse. - You are more likely to get very sick because you are an [older adult](https://www.cdc.gov/aging/covid19/covid19-older-adults.html) or have an [underlying medical condition](https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/people-with-medical-conditions.html). [Possible treatment](https://www.cdc.gov/coronavirus/2019-ncov/your-health/treatments-for-severe-illness.html) may be available for you. - You have questions about your isolation… Since she is older and immunocompromised it is really important to get in touch with her primary care provider right away so that she can be tested to confirm the result and be started on treatments to lessen the disease. These proven treatments need to started in a certain number of days so don’t wait ‘to see if anything bad is going to happen’, contact her doctor today. You should also start techniques like in home masking and isolating to reduce the chances of you catching it while you are caring for her. The CDC site has details about home care when a family member is positive. Call her doctor. Pursue confirmation then supportive treatment. Study home care and prevent you catching it. Take action, time and accurate information matters. ---
**Author:** ![I\_Love\_Me\_Vol.I](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/i_love_me_vol.i/32/521_2.png) [@I\_Love\_Me\_Vol.I](https://boards.straightdope.com/u/I_Love_Me_Vol.I)\ **Post date:** [April 4, 2022, 10:03pm UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/7 "2022-04-04T22:03:44Z")
Has anyone even had a fourth booster? Aren’t we just now starting the second boosters? ---
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [April 4, 2022, 10:32pm UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/8 "2022-04-04T22:32:38Z")
Yeah - I meant 4th shot, 2nd booster. We’re a bit frazzled right now. ---
**Author:** ![I\_Love\_Me\_Vol.I](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/i_love_me_vol.i/32/521_2.png) [@I\_Love\_Me\_Vol.I](https://boards.straightdope.com/u/I_Love_Me_Vol.I)\ **Post date:** [April 4, 2022, 10:35pm UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/9 "2022-04-04T22:35:34Z")
I should think so! Good luck with it. ---
**Author:** ![nearwildheaven](https://avatars.discourse-cdn.com/v4/letter/n/90db22/32.png) [@nearwildheaven](https://boards.straightdope.com/u/nearwildheaven)\ **Post date:** [April 4, 2022, 10:43pm UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/10 "2022-04-04T22:43:10Z")
Which reminds me - I’m planning to get my first booster tomorrow. I’ll need to get my vax card and bring it with me. ---
**Author:** ![Zyada](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zyada/32/3028_2.png) [@Zyada](https://boards.straightdope.com/u/Zyada)\ **Post date:** [April 6, 2022, 12:14am UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/11 "2022-04-06T00:14:50Z")
Huh. My doctor told me that someone who had gotten vaxxed would always test positive. I trust y’all more. ETA, maybe a different test? ---
**Author:** ![JKellyMap](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jkellymap/32/15880_2.png) [@JKellyMap](https://boards.straightdope.com/u/JKellyMap)\ **Post date:** [April 6, 2022, 12:30am UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/12 "2022-04-06T00:30:58Z")
> [@Zyada](#): > > My doctor told me that someone who had gotten vaxxed would always test positive. What??? Are you sure your doctor said this nonsense? ---
**Author:** ![Fretful\_Porpentine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fretful_porpentine/32/2873_2.png) [@Fretful\_Porpentine](https://boards.straightdope.com/u/Fretful_Porpentine)\ **Post date:** [April 6, 2022, 1:10am UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/13 "2022-04-06T01:10:06Z")
> [@Zyada](#): > > Huh. My doctor told me that someone who had gotten vaxxed would always test positive. > > I trust y’all more. > > ETA, maybe a different test? An antibody test, maybe? That would make more sense. ---
**Author:** ![Zyada](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zyada/32/3028_2.png) [@Zyada](https://boards.straightdope.com/u/Zyada)\ **Post date:** [April 7, 2022, 2:54am UTC](https://boards.straightdope.com/t/does-the-4th-booster-ever-cause-a-positive-test/962241/14 "2022-04-07T02:54:22Z")
Yes, because I just had my first incident of deep vein thrombosis. We were discussing what could have caused it, because no one in my family has ever had it, and my sitting habits haven’t changed. But I may have had a very mild case recently.