Home Health Knowing Oxford/AstraZeneca COVID-19 Vaccine

Knowing Oxford/AstraZeneca COVID-19 Vaccine

by Ellon Labana

By Henrylito D. Tacio

Photo Credit: Luca Zennaro/EPA/EFE/Shutterstock

During the early stage of the coronavirus disease 2019 (COVID-19) pandemic, it was apparent that to end the global crisis, vaccines must be developed and available to every person all over the world.

So, in April last year, the international community came together and the COVAX Initiative for equitable global access to COVID-19 vaccines came into existence. The objective was to ensure that people in all corners of the world will get access to COVID-19 vaccines once they are available, regardless of their wealth.

“COVAX participating countries are preparing to receive and use vaccines,” said a joint statement issued by WHO and United Nations Children’s Fund (UNICEF). “Health workers have been trained and cold chain systems primed.”

But what’s missing, as the statement admitted, “is the equitable supply of vaccines.”

“Of the 128 million vaccine doses administered so far, more than three quarters of those vaccinations are in just 10 countries that account for 60% of global GDP,” the two United Nations agencies pointed out. 

The statement said that as of February 10, “almost 130 countries, with 2.5 billion people, are yet to administer a single dose.”

There are several COVID-19 vaccines now available.  One of these is the Oxford/AstraZeneca, known as AZD1222.  “It is made from a weakened version of a common cold virus (known as adenovirus) from chimpanzees,” BBC News reported. “It has been modified to look more like coronavirus – although it can’t cause illness.

“Once injected,” the BBC News stated, “it teaches the body’s immune system how to fight the real virus, should it need to.”

The AZD1222 is one of the COVID-19 vaccines being considered for national immunization in the Philippines. “The private sector and local government units will issue an advance payment for 20 percent for the AstraZeneca COVID-19 vaccines it ordered,” the Philippine Daily Inquirer reported, quoting an interview with vaccine czar Carlito Galvez Jr. on ABS-CBN News Channel.

Last February 11, the WHO Strategic Advisory Group of Experts on Immunization (SAGE) issued interim recommendations for use of this vaccine.

The SAGE is charged with advising WHO on overall global policies and strategies, ranging from vaccines and technology, research and development, to delivery of immunization and its linkages with other health interventions.

Since the vaccine supplies are still limited, the SAGE recommends that priority be given to health workers at high risk of exposure and older people, including those aged 65 or older.

Others who can also take the vaccine include persons with comorbidities that have been identified as increasing the risk of severe COVID-19, including obesity, cardiovascular disease, respiratory disease and diabetes. 

Although further studies are required for persons living with HIV or auto-immune conditions or who are immunocompromised, people in this category who are part of a group recommended for vaccination may be vaccinated after receiving information and counselling. 

Vaccination can be offered to people who have had COVID-19 in the past. But individuals may wish to defer their own COVID-19 vaccination for up to six months from the time of SARS-CoV-2 infection, to allow others who may need the vaccine more urgently to go first.

Vaccination can be offered to breastfeeding women if they are part of a group prioritized for vaccination. The United Nations does not recommend discontinuation of breastfeeding after vaccination. 

What if the woman is still pregnant?  While pregnancy puts women at higher risk of severe COVID-19, the SAGE admits that “very little data are available to assess vaccine safety in pregnancy.”

The press statement said that pregnant women may receive the vaccine “if the benefit of vaccinating a pregnant woman outweighs the potential vaccine risks.”

For this reason, pregnant women at high risk of exposure to SARS-CoV-2 (that is, health workers) or who have comorbidities which add to their risk of severe disease, may be vaccinated “in consultation with their health care provider.”

But not all can take the vaccine.  People with a history of severe allergic reaction to any component of the vaccine should not take it.  In addition, the vaccine is not recommended for persons younger than 18 years of age pending the results of further studies.

The recommended dosage is two doses given intramuscularly (0.5ml each) with an interval of 8 to 12 weeks.  Additional research is still needed to understand longer-term potential protection after a single dose. 

The big question: Is AZD1222 safe?  While this vaccine has yet to be recommended for an Emergency Use Listing by WHO, it has undergone review by the European Medicines Agency (EMA) and consequently meets WHO’s criteria for SAGE consideration.

The EMA has thoroughly assessed the data on the quality, safety and efficacy of the vaccine and has recommended granting a conditional marketing authorization for people aged 18 and above. 

In addition, the Global Advisory Committee on Vaccine Safety, a group of experts that provides independent and authoritative guidance to the WHO on the topic of safe vaccine use, receives and assesses reports of suspected safety events of potentially international impact.

According to SAGE, the AZD1222 vaccine against COVID-19 has an efficacy of 63.09% against symptomatic SARS-CoV-2 infection.  Longer dose intervals within the 8 to 12 weeks range, it added, are associated with greater vaccine efficacy.

Another big question: Does it work against new variants? SAGE reportedly has reviewed all available data on the performance of the vaccine in the settings of variants of concern. The SAGE currently recommends the use of AZD1222 vaccine according to the WHO Prioritization Roadmap, even if virus variants are present in a country. Countries should assess the risks and benefits taking into consideration their epidemiological situation.

Preliminary findings highlight the urgent need for a coordinated approach for surveillance and evaluation of variants and their potential impact on vaccine effectiveness. As new data become available, WHO will update recommendations accordingly.

Right now, there is no substantive data available related to impact of AZD1222 on transmission or viral shedding.

“In the meantime, we must maintain and strengthen public health measures that work: masking, physical distancing, handwashing, respiratory and cough hygiene, avoiding crowds, and ensuring good ventilation,” the SAGE urges.

Meanwhile, the number of reported cases of COVID-19 globally has declined for the fourth week in a row, and the number of deaths also fell for the second consecutive week, according to WHO Director-General Dr. Tedros Adhanom Ghebreyesus in a news conference in Geneva.

“These declines appear to be due to countries implementing public health measures more stringently,” he said.  “We should all be encouraged, but complacency is as dangerous as the virus itself. Now is not the time for any country to relax measures, or for any individual to let down their guard.

“Every life that is lost now is all the more tragic as vaccines are beginning to be rolled out,” he added.  “Alongside traditional public health measures, how quickly we can collectively expand vaccine manufacturing and roll out vaccines to all countries will determine how soon we control the pandemic.”

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