The COVID-19 vaccine is a biological product designed to prevent infection with the novel coronavirus, primarily by stimulating the human immune system to produce antibodies, thereby reducing the risk of infection and severe illness. This vaccine was urgently developed following the global pandemic outbreak in 2020 and has become a core medical tool in controlling the spread of the disease. Currently, billions of doses have been administered worldwide, demonstrating its significant role in public health.
The main goal of the vaccine is to establish herd immunity by reducing the viral transmission chain through mass vaccination. Its mechanism differs from traditional vaccines by utilizing emerging technologies such as mRNA or viral vector platforms, enabling rapid development of highly efficient immune induction systems.
mRNA vaccines like BNT162b2 and mRNA-1273 instruct cells to produce the viral surface spike protein, inducing B cells to generate neutralizing antibodies. Viral vector vaccines such as the AstraZeneca (AZ) vaccine use modified adenoviruses as vectors to deliver the Spike gene into human cells for antigen expression.
Protein subunit vaccines like Novavax directly inject viral protein fragments, combined with adjuvants to enhance immune responses. All vaccine types trigger T-cell memory responses, forming long-term immunity. Antibody production begins approximately two weeks after vaccination, with protection rates exceeding 90% after two doses.
The primary target population is individuals aged 18 and above who have not been infected, although some vaccines have expanded to include those aged 12 and above. Priority is given to high-risk groups such as healthcare workers, patients with chronic illnesses, and residents of long-term care facilities. Special populations like pregnant women should receive vaccination after medical evaluation.
For those who have been infected with the Omicron variant, booster doses can further enhance cross-protection against new variants. Currently, it is recommended to administer the first booster six months after completing the primary series.
The vaccine is typically administered via intramuscular injection in the upper arm. The interval between doses varies: 3-4 weeks for BNT and Moderna vaccines, and 8-12 weeks for AZ. The primary series usually consists of two doses, with subsequent booster doses given at the same dosage as the initial doses.
Special formulations, such as pediatric doses, are one-third of the adult dose and require specific syringes for accurate administration. Post-vaccination observation for 15-30 minutes at the vaccination site is necessary to monitor for acute allergic reactions.
It has been proven to significantly reduce hospitalization and ICU utilization rates, maintaining baseline protection against variants such as Delta and Omicron. Heterologous vaccination (mixing different platforms) can enhance cross-immunity.
Common local reactions include pain and redness at the injection site; systemic reactions such as fever and headache typically last 1-3 days. Rarely, myocarditis risk increases, especially in young males after the second dose.
Severe allergic reactions (anaphylaxis) occur at a rate of approximately 2-5 cases per million doses, so a 30-minute observation period post-vaccination is required. Individuals allergic to vaccine components like polyethylene glycol (PEG) should avoid mRNA vaccines.
Contraindications include severe allergy to the first dose, acute febrile illness, or uncontrolled epilepsy. Immunocompromised individuals (such as those with late-stage HIV or post-organ transplantation) should evaluate the expected vaccine response. Basic preventive measures should continue after vaccination.
Pregnant women should receive vaccination postpartum; breastfeeding women can be vaccinated after informing their healthcare provider. Those on immunosuppressive therapy should assess the timing and dosage with their physician.
It is recommended to space other vaccines at least 14 days apart. For monoclonal antibody treatments, a interval of over 90 days is advised. Patients on immunosuppressants may require additional doses or booster shots.
There are no direct interactions with antiviral drugs like Paxlovid, but concurrent use may affect vaccine immune responses. It is important to inform your healthcare provider of medications taken within the past three months before vaccination.
Phase III clinical trials show that mRNA vaccines provide 95% protection against symptomatic infection and nearly 100% against severe disease. Real-world studies confirm that booster doses restore protection against Omicron BA.1 to over 80%. Long-term follow-up indicates antibody levels decline after six months, but memory B cells can respond rapidly. Mixing different platforms can induce broader antigen recognition.
Unvaccinated individuals can use monoclonal antibodies or antiviral drugs (like Paxlovid) for post-exposure prophylaxis, but such medications must be used within 96 hours of exposure and may be less effective against variants. Natural infection provides immunity lasting about six months, while booster doses can extend protection beyond 12 months. Currently, no approved oral or nasal spray vaccines are available.
Local redness or mild fever are common reactions that usually resolve within 2-3 days. Applying cold compresses can relieve redness and swelling. If body temperature exceeds 38.5°C, take antipyretics as advised by your doctor. Seek medical attention if symptoms persist beyond 48 hours or if you experience difficulty breathing or other abnormal symptoms.
Do I still need to wear a mask and maintain social distancing after vaccination?Yes, even after vaccination, it is recommended to wear masks and keep social distancing in public places, as vaccines do not completely eliminate the risk of infection. Vaccination mainly reduces severe illness and death, but transmission can still occur, so other protective measures should be maintained.
Should I adjust my diet or exercise habits before and after vaccination?No specific adjustments are necessary, but avoid fasting or excessive fatigue on the day of vaccination. If you are on medication for chronic illnesses, continue as usual unless instructed otherwise by your healthcare provider. Normal activities can be resumed after vaccination, but strenuous exercise should be avoided immediately to prevent discomfort.
How long does vaccine protection last, and is a booster needed?The strength and duration of protection vary by vaccine type, with some waning after six months. Health authorities recommend booster doses based on ongoing research, and selecting the current recommended vaccine type can enhance immune memory.
What precautions should I take if exposed to a confirmed COVID-19 case after vaccination?Post-exposure, vaccinated individuals should monitor their health and follow health authority guidelines for quarantine or PCR testing. Report symptoms immediately and follow medical instructions to reduce transmission risk.
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