Breakthrough Covid-19 Infections

                            Dr. KS Dhillon

A vaccine breakthrough infection is defined as the detection of SARS-CoV-2 RNA or antigen in a respiratory specimen collected from a person 14 or more days after they have completed all recommended doses of a COVID-19 vaccine.

We are all aware that COVID-19 vaccines are a critical tool for controlling the ongoing global pandemic. In large, randomized-controlled trials, some vaccines have been found to be safe and efficacious in preventing symptomatic, laboratory-confirmed COVID-19. Despite the relatively high level of vaccine efficacy, a small percentage of fully vaccinated persons do develop symptomatic or asymptomatic infections with SARS-CoV-2, the virus that causes COVID-19.

In the USA as of 30th April 2021, a total of 10,262 SARS-CoV-2 vaccine breakthrough infections had been reported from 46 U.S. states and territories. Sixty-three percent of the cases occurred in females, and the median patient age was 58 years (range = 40–74 years). Twenty-seven percent of vaccine breakthrough infections were asymptomatic, 10% of the patients were hospitalized, and 2% of patients died. Among the 995 patients who were hospitalized 29% were asymptomatic and they were hospitalized for a reason unrelated to COVID-19. The median age of patients who died was 82 years (range = 71–89 years). 

The percent of patients who develop breakthrough infections is small in vaccinated individuals. The breakthrough infections in vaccinated individuals range from 0.2% to 5.9% of the total Covid-19 infections according to statistics from various states in the USA. Ninety-four to 99.8% of the infections occur in non-vaccinated individuals.

The number of breakthrough infection cases are probably underreported because the national surveillance system in the USA relies on passive and voluntary reporting, and data might not be complete or representative. Many individuals with vaccine breakthrough infections, especially those who are asymptomatic or who experience mild illness, might not go for testing. 

A review of Veterans Health Administration (VHA) medical records in the USA pertaining to COVID-19 breakthrough infections in Veterans with spinal cord injuries and disorders (SCI/D), showed that 17 out of 8,319 (0.20%) fully vaccinated Veterans with SCI/D had breakthrough infection as of April 20, 2021. Of those diagnosed with COVID-19 breakthrough infections, 6 (35.3%) were symptomatic and 11(64.7%) were asymptomatic. Of the six symptomatic cases, three were of mild severity, one was moderate, and two were severe. Three patients were hospitalized, and one patient died within 30 days of COVID-19 diagnosis.

A study was carried out at the largest medical center in Israel, to identify breakthrough infections among health care workers. Among 1,497 fully vaccinated health care workers, 39 SARS-CoV-2 (2.6%) breakthrough infections were detected. 

Most breakthrough cases were mild or asymptomatic, although 19% had persistent symptoms lasting more than 6 weeks. The alpha variant was found in 85% of the samples tested. 

A study was carried out in India to ascertain the number of breakthrough COVID19 infections after vaccinations in a chronic care, diabetes-centric healthcare facility. One hundred and seven (94.7%) out of 123 employees had completed their 2nd dose of vaccination. Symptomatic breakthrough infections after 14 days of the second dose occurred in 15 persons (13.3%). All 14 had mild COVID19 disease.  Symptoms lasted from 3 to 14 days. One patient required hospitalization for pneumonia. 

The Chicago Department of Public Health (CDPH) carried out a study to identify breakthrough infections among skilled nursing facility residents and staff members in Chicago, Illinois, between December 2020 and March 2021.

There were 627 persons with SARS-CoV-2 infection across 75 SNFs.  Breakthrough infections occurred in 12 residents and 10 staff members accounted for 16% (22 of 136) of the COVID-19 infections. Nearly two-thirds (14 of 22; 64%) of persons with breakthrough infections were asymptomatic; two residents were hospitalized because of COVID-19, and one died.

In the USA as of 2nd August 2021, more than 164 million people had been fully vaccinated against Covid-19. According to data from CDC, there have been 7,101 hospitalizations and 1,507 deaths due to breakthrough infections. Individuals who are fully vaccinated and develop breakthrough infections usually develop mild to moderate illness, if they develop symptoms at all.

Vaccines shorten the length of illness in individuals who develop breakthrough infections. Vaccination reduces disease severity and duration of illness in individuals who develop breakthrough infections. 

Previously, scientists believed that vaccinated individuals rarely transmitted the virus. However, the Delta variant has changed the game. Emerging evidence shows that vaccinated individuals can spread the Delta variant to some extent. Unvaccinated individuals transmit the virus at a higher rate than vaccinated individuals.

Individuals with weakened immune system are at higher risk of getting  breakthrough infection because the vaccines work less well for them. Immunocompromised individuals include organ transplant recipients, cancer patients, and those with advanced HIV or uncontrolled diabetes. Upto 46% of patients who had received solid organ transplants do not mount an antibody response after two doses of an mRNA vaccine. A booster shot may be required for immunocompromised individuals.

Older individuals are more at risk of developing severe complications from breakthrough infections. Around three-quarters of breakthrough infections that caused hospitalizations or deaths occur in those aged 65 and older.

Overall, the data in the USA, showed that approximately 1 in 900 vaccinated people had breakthrough infections. The vast majority of those infected have mild or no symptoms of Covid. About 1 in 17,000 need to be hospitalized. Approximately 1 in 83,000 vaccinated people die from Covid. 

In general, it's very, very rare to get Covid infection after being vaccinated.

Overall about 95% of breakthrough infections are mild and do not require hospitalization.

In Malaysia, the incidence of breakthrough infections is higher than in the USA. Between Aug 12 to Aug 29, 2021, there were 68,629 breakthrough infections comprising 17.8% of the total 385,542 Covid-19 cases. There has been a gradual increase in the percentage of breakthrough infections. On 12 August 2021 the percentage was 12.6% and on 29 August 2021, it was 23.9%. 

There were 8,159 patients in category 3 to 5 who were hospitalized. The percentage of fully vaccinated was 1.6% and 2.2% were not fully vaccinated. The number of ICU admissions of category 4 and 5 patients was 4,762. The percentage of fully vaccinated was 0.8% and not fully vaccinated was 1.3%.

In Malaysia, daily Covid-19 cases increased fourfold from 5,586 on June 27 to 22,070 on 27 August 2021, while daily deaths increased from 60 cases on June 27 to 339 on 27 August. 

As of 27 August 2021, 61.1 percent of the country's adult population had been fully vaccinated, while in the Klang Valley, 88.7 percent of the adult population had been fully immunized. New cases, however, continued to spike in Selangor (from 2,212 cases on June 27 to 5,920 on 27 August) and Kuala Lumpur (628 cases on June 27 to 1,809 on 27/8/21).

Death rates in Selangor also increased from 20 fatalities on June 27 to 103 on 27/8/21. In Kuala Lumpur, it spiked from 16 deaths on June 27 to 40 on 27/8/21.

An end to this pandemic does not appear to be in sight despite the large numbers of individuals having been vaccinated.