{"id":1531,"date":"2021-01-25T08:30:38","date_gmt":"2021-01-25T00:30:38","guid":{"rendered":"https:\/\/asiamd.com\/?p=1531"},"modified":"2025-08-22T18:42:23","modified_gmt":"2025-08-22T18:42:23","slug":"safety-mrna-covid-19-vaccines","status":"publish","type":"post","link":"https:\/\/asiamd.bqubetech.com\/id\/2021\/01\/25\/safety-mrna-covid-19-vaccines\/","title":{"rendered":"Safety of mRNA Covid-19 Vaccines"},"content":{"rendered":"<p><span style=\"font-weight: 400;\">Singaporeans have already been warned: the Government\u2019s aim is to get as many people vaccinated as quickly as possible, so they\u00a0<\/span><a href=\"https:\/\/www.straitstimes.com\/singapore\/health\/covid-19-vaccine-will-not-be-reserved-for-singaporeans-who-choose-to-wait-and-see\"><span style=\"font-weight: 400;\">will not reserve vaccines for those who opt to wait and see<\/span><\/a><span style=\"font-weight: 400;\">. We<\/span><a href=\"https:\/\/asiamd.com\/2021\/01\/12\/all-you-need-to-know-about-covid-19-vaccines-in-singapore\/\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">\u00a0already know<\/span><\/a><span style=\"font-weight: 400;\">\u00a0that Singapore\u2019s national vaccination programme includes only mRNA Covid-19 vaccines from Pfizer-BioNTech and Moderna.<\/span><\/p>\n<blockquote>\n<p class=\"p1\"><a href=\"https:\/\/bit.ly\/AsiaMDWhatsAppEN\" target=\"_blank\" rel=\"noopener\"><b><i>Follow us on WhatsApp for the latest updates: https:\/\/bit.ly\/AsiaMDWhatsAppEN\u00a0<\/i><\/b><\/a><\/p>\n<\/blockquote>\n<p><span style=\"font-weight: 400;\">Both vaccines from\u00a0<\/span><a href=\"https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/different-vaccines\/Pfizer-BioNTech.html\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Pfizer-BioNTech<\/span><\/a><span style=\"font-weight: 400;\">\u00a0and\u00a0<\/span><a href=\"https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/different-vaccines\/Moderna.html\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Moderna<\/span><\/a><span style=\"font-weight: 400;\">\u00a0work via a novel\u00a0<\/span><a href=\"https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/different-vaccines\/mrna.html\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">messenger RNA (mRNA) mechanism<\/span><\/a><span style=\"font-weight: 400;\">. This means that the vaccines teach our cells how to make a protein which triggers an immune response inside our bodies.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In their phase 3 clinical research trial published in the\u00a0<\/span><a href=\"https:\/\/www.nejm.org\/doi\/pdf\/10.1056\/NEJMoa2034577?articleTools=true\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">New England Journal of Medicine (NEJM)<\/span><\/a><span style=\"font-weight: 400;\">\u00a0in Dec 2020, Pfizer-BioNTech\u2019s end-point results showed 95% efficacy in preventing symptomatic Covid-19 infection as defined by this criteria: (1) patient should have at least\u00a0<\/span><b>one<\/b><span style=\"font-weight: 400;\">\u00a0symptom of Covid-19 infection and (2) obtain a positive outcome for a swab PCR test for Covid-19 nucleic-acid within four days of having such symptoms.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">For Moderna, their phase 3 clinical research<\/span><a href=\"https:\/\/www.nejm.org\/doi\/pdf\/10.1056\/NEJMoa2035389\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">\u00a0published in NEJM<\/span><\/a><span style=\"font-weight: 400;\">\u00a0in Dec 2020 defined Covid-19 cases differently. Their end-point results showed 94.1% efficacy in preventing symptomatic Covid-19 infection, which is defined by: (1) having at least\u00a0<\/span><b>two<\/b><span style=\"font-weight: 400;\">\u00a0symptoms of Covid-19 infection and (2) testing positive for swab PCR tests for Covid-19 nucleic-acid at any time.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Prior to June 4, 2021,\u00a0<\/span><a href=\"https:\/\/www.moh.gov.sg\/covid-19\/vaccination#:~:text=About%20Singapore's%20COVID%2D19%20Vaccination%20Programme&amp;text=Vaccination%20is%20free%20to%20all,(e.g.%20persons%20with%20comorbidities).\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">the vaccine task force had adopted a more conservative stance and did not offer the mRNA Covid-19 vaccines to the following<\/span><\/a><span style=\"font-weight: 400;\">:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">pregnant and breastfeeding mothers<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">immunocompromised people (i.e. cancer patients, transplant patients taking immune suppression drugs)<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">people who have a history of anaphylaxis (very severe allergic reactions)<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">those who are severely ill<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">However, these\u00a0<\/span><a href=\"https:\/\/www.todayonline.com\/singapore\/pregnant-women-can-book-covid-19-vaccination-appointments-starting-june-4-safe-breastfeeding-get-jabs-moh\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">vaccination guidelines have since been revised by the task force<\/span><\/a><span style=\"font-weight: 400;\">\u00a0after more people have been vaccinated both globally and locally. These groups of people who were previously ineligible for vaccination can now register themselves:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Pregnant and breastfeeding women<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Cancer patients receiving active treatment<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Persons with drug reactions<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Persons with a history of anaphylaxis<\/span><\/li>\n<\/ul>\n<p><i><span style=\"font-weight: 400;\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-2464\" src=\"https:\/\/asiamd.bqubetech.com\/wp-content\/uploads\/2021\/01\/ExiasaxY9XRfR-Q3mzZANz-50VBoc2d77YYbXUoDuXhtn38_r91RnFzPpSd6KbDP8LAWj7YqINEqwVmVxwoR9AxUiXOHgSqMG5alWC7_1PK1R4j1bsjrPDslaT6-v7PFd.jpg\" alt=\"\" width=\"1081\" height=\"1351\" \/>Image:\u00a0<\/span><\/i><a href=\"https:\/\/www.todayonline.com\/singapore\/pregnant-women-can-book-covid-19-vaccination-appointments-starting-june-4-safe-breastfeeding-get-jabs-moh\" target=\"_blank\" rel=\"noopener\"><i><span style=\"font-weight: 400;\">todayonline.com<\/span><\/i><\/a><\/p>\n<p><span style=\"font-weight: 400;\">There may be other burning medical questions bugging you, such as: Do the vaccines prevent transmission of the virus to others? What do we know about each of the vaccines?<\/span><\/p>\n<p><span style=\"font-weight: 400;\">If you\u2019re looking for further reading on the vaccines\u2019 short-term and long-term safety, we found a handy resource that can help. Infectious disease specialist, Professor Paul Sax from Harvard Medical School, has given detailed answers to some frequently asked questions about the mRNA vaccines, which were the\u00a0<\/span><a href=\"https:\/\/www.bbc.com\/news\/world-us-canada-55370999\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">first Covid-19 vaccines to have been approved for use in the United States<\/span><\/a><span style=\"font-weight: 400;\">. We\u2019ve picked 12 questions that may have crossed your mind. For full details, please refer to the\u00a0<\/span><a href=\"https:\/\/www.nejm.org\/covid-vaccine\/faq\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">original NEJM article<\/span><\/a><span style=\"font-weight: 400;\">. Please note that the medical recommendations from the\u00a0<\/span><a href=\"https:\/\/www.cdc.gov\/\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Centers for Disease Control and Prevention (CDC) in the United States<\/span><\/a><span style=\"font-weight: 400;\">\u00a0may diverge from the\u00a0<\/span><a href=\"https:\/\/www.moh.gov.sg\/covid-19\/vaccination#:~:text=About%20Singapore's%20COVID%2D19%20Vaccination%20Programme&amp;text=Vaccination%20is%20free%20to%20all,(e.g.%20persons%20with%20comorbidities).\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">guidelines issued by Singapore\u2019s vaccine task force<\/span><\/a><span style=\"font-weight: 400;\">.<\/span><\/p>\n<ol>\n<li><b> Do we still need to mask up, wash our hands and socially distance after receiving the vaccines?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">At the moment, doctors do not know whether the vaccines completely prevent asymptomatic infection and inadvertently cause people to become carriers of the Covid-19 virus. Since up to 40% of people who get infected with SARS-CoV-2 have no symptoms but may still transmit the virus to others, this is a theoretical concern. Therefore, vaccination does not allow everyone to halt all important precautionary measures such as wearing masks, practising social distancing, avoiding crowded indoor settings and regular hand washing.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The protective effect from vaccines will never be 100%. These caveats notwithstanding, doctors say that these vaccines will reduce the capacity to transmit the virus to others.<\/span><\/p>\n<ol start=\"2\">\n<li><b> What do we know about each of the vaccines\u2019 short-term\u00a0<\/b><b><i>and\u00a0<\/i><\/b><b>long-term safety?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\"><br \/>\n<\/span><span style=\"font-weight: 400;\">The most common short-term side effect is pain at the injection site, especially 12 to 24 hours after the jab. Around 1% of participants in the trials categorised the pain as \u201csevere.\u201d Other relatively common side effects include fatigue and headache. High fevers are less common. These side effects generally resolve within a couple of days and are responsive to paracetamol or a nonsteroidal anti-inflammatory drug such as ibuprofen.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In general, side effects are more common in younger vaccine recipients than in older ones, with the second shot inducing more side effects than the first dose.<\/span><\/p>\n<p><a href=\"https:\/\/www.mayoclinic.org\/diseases-conditions\/bells-palsy\/symptoms-causes\/syc-20370028\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Bell\u2019s palsy<\/span><\/a><span style=\"font-weight: 400;\">\u00a0was reported more frequently in vaccine recipients than in controls, but there was not a sufficiently large number of cases to conclude that this was beyond what would naturally be observed in populations of this size by chance. There were no cases of\u00a0<\/span><a href=\"https:\/\/www.mayoclinic.org\/diseases-conditions\/guillain-barre-syndrome\/symptoms-causes\/syc-20362793#:~:text=Guillain%2DBarre%20(gee%2DYAH,eventually%20paralyzing%20your%20whole%20body.\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Guillain\u2013Barr\u00e9<\/span><\/a><span style=\"font-weight: 400;\">\u00a0syndrome or\u00a0<\/span><a href=\"https:\/\/www.mayoclinic.org\/diseases-conditions\/transverse-myelitis\/symptoms-causes\/syc-20354726#:~:text=Transverse%20myelitis%20is%20an%20inflammation,nerves%20send%20throughout%20the%20body.\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">transverse myelitis<\/span><\/a><span style=\"font-weight: 400;\">.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">However, there have been\u00a0<\/span><a href=\"https:\/\/www.nejm.org\/doi\/full\/10.1056\/NEJMra2035343\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">reports of vaccine recipients experiencing severe allergic reactions (anaphylaxis)<\/span><\/a><span style=\"font-weight: 400;\">\u00a0shortly after receiving their first dose in the United Kingdom and the United States. The current leading suspect in causing these reactions is polyethylene glycol, a compound present in both the Pfizer-BioNTech and Moderna vaccines.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">It\u2019s critically important to emphasise that these allergic reactions are uncommon \u2014 the current estimate is that anaphylaxis will occur at\u00a0<\/span><a href=\"https:\/\/www.cdc.gov\/mmwr\/volumes\/70\/wr\/mm7002e1.htm\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">approximately 1 in 100,000 doses<\/span><\/a><span style=\"font-weight: 400;\">. Although this rate of severe allergic reactions is higher than that with other vaccines, it is substantially lower than the rate reported with penicillin, which is estimated to be 1 in 5000.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">As for the long-term side effects, the short answer is that doctors do not know yet. The remarkably fast pace of vaccine development means that medical professionals have had only months, not years of follow-up. Both the Pfizer-BioNTech and Moderna vaccines, which work via a\u00a0<\/span><a href=\"https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/different-vaccines\/mrna.html\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">novel messenger RNA (mRNA) mechanism<\/span><\/a><span style=\"font-weight: 400;\">, started only in the summer of 2020.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">But with other immunisations, severe reactions typically occur within days or weeks after administration. Long-term side effects with vaccines are quite rare, with putative associations later debunked by carefully done population-based studies.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Further safety data on both vaccines will be reported to the\u00a0<\/span><a href=\"https:\/\/vaers.hhs.gov\/\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Vaccine Adverse Event Reporting System (VAERS)<\/span><\/a><span style=\"font-weight: 400;\">, a national early warning system in the United States that was set up to detect possible safety problems in any licensed vaccine and has been in operation since 1990.<\/span><\/p>\n<ol start=\"3\">\n<li><b> Are there contraindications to any of the vaccines?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">The only absolute contraindication to these vaccines is known hypersensitivity to the vaccine components. Specific recommendations from the CDC in the US regarding contraindications list the following:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Severe allergic reaction (e.g., anaphylaxis) after a previous dose of an mRNA Covid-19 vaccine or any of its components<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Immediate allergic reaction of any severity to a previous dose of an mRNA Covid-19 vaccine or any of its components (including polyethylene glycol [PEG])<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Immediate allergic reaction of any severity to polysorbate (due to potential cross-reactive hypersensitivity with the vaccine ingredient PEG)<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">In this NEJM report, Dr Sax says that anaphylaxis in reaction to any other vaccine or injectable therapies is not a contraindication to these Covid-19 vaccines, but persons with this history should be observed for at least 30 minutes after they receive their dose.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">If a person experiences a severe reaction (in particular anaphylaxis) to the first shot, the person should not receive the second. People who experience severe pain will need to make an individual decision about whether to proceed with the second shot \u2014 it is not contraindicated, but side effects tend to be worse with the second dose. One potential strategy is to administer acetaminophen or ibuprofen as soon as the pain starts after the second dose. The CDC does not recommend pre-vaccine administration of these drugs, since theoretically they could blunt vaccine-induced antibody responses.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Monoclonal antibodies or convalescent plasma for treatment of Covid-19 could theoretically reduce the efficacy of the vaccines. Anyone who has received these treatments should delay receiving the vaccine for at least 90 days, a duration that factors in both the known half-life of these therapies and the low likelihood that someone with Covid-19 will experience reinfection in this time period. Further discussion of the rationale behind this recommendation has been added to the\u00a0<\/span><a href=\"https:\/\/www.cdc.gov\/vaccines\/covid-19\/info-by-product\/clinical-considerations.html?CDC_AA_refVal=https%3A%2F%2Fwww.cdc.gov%2Fvaccines%2Fcovid-19%2Finfo-by-product%2Fpfizer%2Fclinical-considerations.html\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">clinical considerations from the CDC guidance<\/span><\/a><span style=\"font-weight: 400;\">.<\/span><\/p>\n<ol start=\"4\">\n<li><b> Should immunocompromised patients receive the vaccine?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">The CDC considers immunocompromised patients to be at\u00a0<\/span><a href=\"https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/need-extra-precautions\/immunocompromised.html\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">increased risk for severe Covid-19<\/span><\/a><span style=\"font-weight: 400;\">. This is broadly defined as patients with histories meeting the following criteria, which are not 100% inclusive:<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Cancer<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Bone marrow transplant<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Solid-organ transplant<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Stem cells for cancer treatment<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Genetic immune deficiencies<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">HIV<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Use of oral or intravenous corticosteroids or other medicines called immunosuppressants that lower the body\u2019s ability to fight some infections (e.g., mycophenolate, sirolimus, cyclosporine, tacrolimus, etanercept, rituximab)<\/span><\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">The American Society of Hematology and the American Society for Transplantation and Cellular Therapy\u00a0<\/span><a href=\"https:\/\/www.hematology.org\/covid-19\/ash-astct-covid-19-and-vaccines\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">has a similar list with additional details<\/span><\/a><span style=\"font-weight: 400;\">. Because of the heightened risk of severe Covid-19 in this population, immunocompromised patients should receive the Covid-19 vaccines if there are no contraindications.<\/span><\/p>\n<ol start=\"5\">\n<li><b> Should pregnant or breastfeeding women receive the vaccine?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">Although pregnant and breastfeeding women were not enrolled in the Covid-19 vaccine trials and as a result there are limited data about safety,\u00a0<\/span><a href=\"https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/vaccines\/recommendations\/pregnancy.html\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">the CDC advises that pregnant and lactating women should be offered the vaccine and may choose to be vaccinated<\/span><\/a><span style=\"font-weight: 400;\">. This view is shared by the\u00a0<\/span><a href=\"https:\/\/www.acog.org\/clinical\/clinical-guidance\/practice-advisory\/articles\/2020\/12\/vaccinating-pregnant-and-lactating-patients-against-covid-19\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">American College of Obstetricians and Gynecologists<\/span><\/a><span style=\"font-weight: 400;\">\u00a0and the\u00a0<\/span><a href=\"https:\/\/s3.amazonaws.com\/cdn.smfm.org\/media\/2591\/SMFM_Vaccine_Statement_12-1-20_(final).pdf\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Society for Maternal\u2013Fetal Medicine<\/span><\/a><span style=\"font-weight: 400;\">. There is no theoretical reason why mRNA vaccines would be harmful to the mother during pregnancy, to a developing fetus, or to a breastfeeding infant. Also reassuring is that gestating rats receiving the Moderna vaccine did not demonstrate any safety concerns related to fetal or embryonal development.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Acetaminophen or paracetamol is preferred for diminishing side effects among pregnant women.<\/span><\/p>\n<ol start=\"6\">\n<li><b> Can children receive the vaccine?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">The Pfizer-BioNTech vaccine is now authorised for patients \u226512 years, and the Moderna vaccine for \u226518 years. Clinical trials are under way to test Covid-19 vaccines in children under the age of 12.<\/span><\/p>\n<ol start=\"7\">\n<li><b> How should early side effects be managed?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">Analgesics and antipyretics such as acetaminophen, paracetamol or ibuprofen are effective in managing post-vaccine side effects including injection-site pain, myalgias, and fever. However, the CDC does not recommend pre-vaccine administration of these drugs, as they could theoretically blunt vaccine-induced antibody responses.<\/span><\/p>\n<ol start=\"8\">\n<li><b> Should acetaminophen, paracetamol or nonsteroidal anti-inflammatory drugs be taken prior to vaccination to prevent post-vaccination symptoms?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">Although these drugs could decrease subjective side effects, theoretically they could also blunt immune response and make the vaccines less effective \u2014 hence they are not recommended before vaccination. They are useful, however, in diminishing side effects once they occur.<\/span><\/p>\n<ol start=\"9\">\n<li><b> Should a patient who was exposed to Covid-19 receive the vaccine in order to prevent the disease?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">Currently, there is no data to support use of the Covid-19 vaccines acutely to prevent disease after a known exposure to an active case. Since the incubation period for Covid-19 averages around five days, it is unlikely that the vaccine would elicit an immune response quickly enough to block infection. As a result, people who have been exposed to Covid-19 should finish their 10- to 14-day quarantine before undergoing immunisation. Since some vaccines for other diseases (notably varicella) are effective in preventing infection after exposure, it is possible that this will be a future recommendation for Covid-19 vaccination, but currently it is not.<\/span><\/p>\n<ol start=\"10\">\n<li><b> Should patients who have recovered from Covid-19 receive the vaccine?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">Yes, they should receive the vaccine. Some of the people who participated in the clinical trials had evidence of prior SARS-CoV-2 infection (based on a positive antibody test), and the vaccines were safe and effective in this group.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Since re-infection after recovery from Covid-19 is rare in the first 90 days, some people may wish to defer immunisation for this long \u2014 however, if they wish to be immunised sooner, there is no contraindication. Patients who were treated with monoclonal antibodies or convalescent plasma should wait this long, however. These treatments might inactivate the vaccines, making them less effective. Deferral of immunisation for 90 days after treatment with monoclonal antibodies or convalescent plasma is recommended.<\/span><\/p>\n<ol start=\"11\">\n<li><b> Should a patient who is diagnosed with Covid-19 shortly after the first dose still receive the second scheduled dose?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">The vaccine begins to generate protective immunity 10 to 14 days after the first shot. As a result, it is not surprising that some people have experienced Covid-19 shortly after their first immunisation, and they naturally wonder whether they should proceed with the second shot as originally scheduled.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The current recommendation is that people with current infection should wait until they have recovered from the acute illness and are\u00a0<\/span><a href=\"https:\/\/www.cdc.gov\/coronavirus\/2019-ncov\/hcp\/duration-isolation.html#:~:text=For%20most%20persons%20with%20COVID,with%20improvement%20of%20other%20symptoms.\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">eligible to discontinue isolation<\/span><\/a><span style=\"font-weight: 400;\">. These recommendations apply both to those who developed Covid-19 before their first injection and to those who developed it after starting the vaccine series. On the basis of this guidance, some people in the latter group may be able to proceed with their scheduled second shot and others will need to wait. Treatment of Covid-19 with either monoclonal antibodies or convalescent plasma should delay receipt of the vaccine by 90 days, since these treatments could theoretically make the vaccine less effective.<\/span><\/p>\n<ol start=\"12\">\n<li><b> How does the vaccine affect the evaluation of a patient and diagnostic testing for possible Covid-19?<\/b><\/li>\n<\/ol>\n<p><span style=\"font-weight: 400;\">The Covid-19 vaccines will not influence the results of PCR or antigen testing for the disease. The vaccines generate antibodies to SARS-CoV-2, which are directed at the spike protein.<\/span><\/p>\n<p><b><i>Source:<\/i><\/b><span style=\"font-weight: 400;\">\u00a0<\/span><a href=\"https:\/\/www.nejm.org\/covid-vaccine\/faq\" target=\"_blank\" rel=\"noopener\"><span style=\"font-weight: 400;\">Covid-19 Vaccine \u2014 Frequently Asked Questions, The New England Journal of Medicine, by Paul Sax, M.D., a Professor of Medicine at Harvard Medical School and an infectious disease specialist.<\/span><\/a><\/p>\n<p><span style=\"font-weight: 400;\">Disclaimer: This article was compiled based on Dr Sax\u2019s views, which were published by the editor of the prestigious New England Journal of Medicine. Actual practice and guidelines pertaining to Covid-19 vaccinations in Singapore may differ from Dr Sax\u2019s recommendations.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>What do doctors know about the safety of the mRNA Covid-19 vaccines developed by Pfizer-BioNTech and Moderna? 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