Measuring the efficacy of a vaccine during an epidemic. 2023

Antonio Scala, and Pierpaolo Cavallo
CNR-ISC, Applico Lab, Roma, Italy.

The urgency to develop vaccines during the COVID-19 pandemic has resulted in the acceleration of clinical trials. Specifically, a broad spectrum of efficacy levels has been reported for various vaccines based on phase III cohort studies. Our study demonstrates that conducting large cohort phase III clinical trials during the peak of an epidemic leads to a significant underestimation of vaccine efficacy, even in the absence of confounding factors. Furthermore, we find that this underestimation increases with the proportion of infectious individuals in the population during the experiment and the severity of the epidemic, as measured by its basic reproduction number.

UI MeSH Term Description Entries
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000054 Acceleration An increase in the rate of speed. Accelerations
D000086382 COVID-19 A viral disorder generally characterized by high FEVER; COUGH; DYSPNEA; CHILLS; PERSISTENT TREMOR; MUSCLE PAIN; HEADACHE; SORE THROAT; a new loss of taste and/or smell (see AGEUSIA and ANOSMIA) and other symptoms of a VIRAL PNEUMONIA. In severe cases, a myriad of coagulopathy associated symptoms often correlating with COVID-19 severity is seen (e.g., BLOOD COAGULATION; THROMBOSIS; ACUTE RESPIRATORY DISTRESS SYNDROME; SEIZURES; HEART ATTACK; STROKE; multiple CEREBRAL INFARCTIONS; KIDNEY FAILURE; catastrophic ANTIPHOSPHOLIPID ANTIBODY SYNDROME and/or DISSEMINATED INTRAVASCULAR COAGULATION). In younger patients, rare inflammatory syndromes are sometimes associated with COVID-19 (e.g., atypical KAWASAKI SYNDROME; TOXIC SHOCK SYNDROME; pediatric multisystem inflammatory disease; and CYTOKINE STORM SYNDROME). A coronavirus, SARS-CoV-2, in the genus BETACORONAVIRUS is the causative agent. 2019 Novel Coronavirus Disease,2019 Novel Coronavirus Infection,2019-nCoV Disease,2019-nCoV Infection,COVID-19 Pandemic,COVID-19 Pandemics,COVID-19 Virus Disease,COVID-19 Virus Infection,Coronavirus Disease 2019,Coronavirus Disease-19,SARS Coronavirus 2 Infection,SARS-CoV-2 Infection,Severe Acute Respiratory Syndrome Coronavirus 2 Infection,COVID19,2019 nCoV Disease,2019 nCoV Infection,2019-nCoV Diseases,2019-nCoV Infections,COVID 19,COVID 19 Pandemic,COVID 19 Virus Disease,COVID 19 Virus Infection,COVID-19 Virus Diseases,COVID-19 Virus Infections,Coronavirus Disease 19,Disease 2019, Coronavirus,Disease, 2019-nCoV,Disease, COVID-19 Virus,Infection, 2019-nCoV,Infection, COVID-19 Virus,Infection, SARS-CoV-2,Pandemic, COVID-19,SARS CoV 2 Infection,SARS-CoV-2 Infections,Virus Disease, COVID-19,Virus Infection, COVID-19
D014612 Vaccines Suspensions of killed or attenuated microorganisms (bacteria, viruses, fungi, protozoa), antigenic proteins, synthetic constructs, or other bio-molecular derivatives, administered for the prevention, amelioration, or treatment of infectious and other diseases. Vaccine
D050936 Basic Reproduction Number The expected number of new cases of an infection caused by an infected individual, amongst susceptible contacts only. Basic Reproductive Number,Basic Reproductive Ratio,Effective Reproduction Number,Effective Reproductive Number,R0 Basic Reproduction Number,RE Effective Reproduction Number,Re Effective Reproductive Number,Transmissibility Measures,Basic Reproduction Ratio,Basic Reproductive Rate,Basic Reproductive Numbers,Basic Reproductive Rates,Basic Reproductive Ratios,Effective Reproduction Numbers,Effective Reproductive Numbers,Rate, Basic Reproductive,Reproduction Number, Basic,Reproduction Number, Effective,Reproduction Ratio, Basic,Reproductive Number, Basic,Reproductive Number, Effective,Reproductive Rate, Basic,Reproductive Rates, Basic,Reproductive Ratio, Basic,Transmissibility Measure
D058873 Pandemics Epidemics of infectious disease that have spread to many countries, often more than one continent, and usually affecting a large number of people. Pandemic

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